Sphinx 2.0.8-release reference manual
=====================================

Free open-source SQL full-text search engine
============================================

Copyright (c) 2001-2013 Andrew Aksyonoff

Copyright (c) 2008-2013 Sphinx Technologies Inc, http://sphinxsearch.com

----------------------------------------------------------------------------

Table of Contents

1. Introduction
   1.1. About
   1.2. Sphinx features
   1.3. Where to get Sphinx
   1.4. License
   1.5. Credits
   1.6. History

2. Installation
   2.1. Supported systems
   2.2. Required tools
   2.3. Installing Sphinx on Linux
   2.4. Installing Sphinx on Windows
   2.5. Known installation issues
   2.6. Quick Sphinx usage tour

3. Indexing
   3.1. Data sources
   3.2. Full-text fields
   3.3. Attributes
   3.4. MVA (multi-valued attributes)
   3.5. Indexes
   3.6. Restrictions on the source data
   3.7. Charsets, case folding, and translation tables
   3.8. SQL data sources (MySQL, PostgreSQL)
   3.9. xmlpipe data source
   3.10. xmlpipe2 data source
   3.11. Live index updates
   3.12. Delta index updates
   3.13. Index merging

4. Real-time indexes
   4.1. RT indexes overview
   4.2. Known caveats with RT indexes
   4.3. RT index internals
   4.4. Binary logging

5. Searching
   5.1. Matching modes
   5.2. Boolean query syntax
   5.3. Extended query syntax
   5.4. Search results ranking
   5.5. Expressions, functions, and operators
      5.5.1. Operators
      5.5.2. Numeric functions
      5.5.3. Date and time functions
      5.5.4. Type conversion functions
      5.5.5. Comparison functions
      5.5.6. Miscellaneous functions

   5.6. Sorting modes
   5.7. Grouping (clustering) search results
   5.8. Distributed searching
   5.9. searchd query log formats
      5.9.1. Plain log format
      5.9.2. SphinxQL log format

   5.10. MySQL protocol support and SphinxQL
   5.11. Multi-queries
   5.12. Collations
   5.13. User-defined functions (UDF)

6. Command line tools reference
   6.1. indexer command reference
   6.2. searchd command reference
   6.3. search command reference
   6.4. spelldump command reference
   6.5. indextool command reference

7. SphinxQL reference
   7.1. SELECT syntax
   7.2. SHOW META syntax
   7.3. SHOW WARNINGS syntax
   7.4. SHOW STATUS syntax
   7.5. INSERT and REPLACE syntax
   7.6. DELETE syntax
   7.7. SET syntax
   7.8. SET TRANSACTION syntax
   7.9. BEGIN, COMMIT, and ROLLBACK syntax
   7.10. CALL SNIPPETS syntax
   7.11. CALL KEYWORDS syntax
   7.12. SHOW TABLES syntax
   7.13. DESCRIBE syntax
   7.14. CREATE FUNCTION syntax
   7.15. DROP FUNCTION syntax
   7.16. SHOW VARIABLES syntax
   7.17. SHOW COLLATION syntax
   7.18. UPDATE syntax
   7.19. ATTACH INDEX syntax
   7.20. FLUSH RTINDEX syntax
   7.21. Multi-statement queries
   7.22. Comment syntax
   7.23. List of SphinxQL reserved keywords
   7.24. SphinxQL upgrade notes, version 2.0.1-beta

8. API reference
   8.1. General API functions
      8.1.1. GetLastError
      8.1.2. GetLastWarning
      8.1.3. SetServer
      8.1.4. SetRetries
      8.1.5. SetConnectTimeout
      8.1.6. SetArrayResult
      8.1.7. IsConnectError

   8.2. General query settings
      8.2.1. SetLimits
      8.2.2. SetMaxQueryTime
      8.2.3. SetOverride
      8.2.4. SetSelect

   8.3. Full-text search query settings
      8.3.1. SetMatchMode
      8.3.2. SetRankingMode
      8.3.3. SetSortMode
      8.3.4. SetWeights
      8.3.5. SetFieldWeights
      8.3.6. SetIndexWeights

   8.4. Result set filtering settings
      8.4.1. SetIDRange
      8.4.2. SetFilter
      8.4.3. SetFilterRange
      8.4.4. SetFilterFloatRange
      8.4.5. SetGeoAnchor

   8.5. GROUP BY settings
      8.5.1. SetGroupBy
      8.5.2. SetGroupDistinct

   8.6. Querying
      8.6.1. Query
      8.6.2. AddQuery
      8.6.3. RunQueries
      8.6.4. ResetFilters
      8.6.5. ResetGroupBy

   8.7. Additional functionality
      8.7.1. BuildExcerpts
      8.7.2. UpdateAttributes
      8.7.3. BuildKeywords
      8.7.4. EscapeString
      8.7.5. Status
      8.7.6. FlushAttributes

   8.8. Persistent connections
      8.8.1. Open
      8.8.2. Close

9. MySQL storage engine (SphinxSE)
   9.1. SphinxSE overview
   9.2. Installing SphinxSE
      9.2.1. Compiling MySQL 5.0.x with SphinxSE
      9.2.2. Compiling MySQL 5.1.x with SphinxSE
      9.2.3. Checking SphinxSE installation

   9.3. Using SphinxSE
   9.4. Building snippets (excerpts) via MySQL

10. Reporting bugs
11. sphinx.conf options reference
   11.1. Data source configuration options
      11.1.1. type
      11.1.2. sql_host
      11.1.3. sql_port
      11.1.4. sql_user
      11.1.5. sql_pass
      11.1.6. sql_db
      11.1.7. sql_sock
      11.1.8. mysql_connect_flags
      11.1.9. mysql_ssl_cert, mysql_ssl_key, mysql_ssl_ca
      11.1.10. odbc_dsn
      11.1.11. sql_query_pre
      11.1.12. sql_query
      11.1.13. sql_joined_field
      11.1.14. sql_query_range
      11.1.15. sql_range_step
      11.1.16. sql_query_killlist
      11.1.17. sql_attr_uint
      11.1.18. sql_attr_bool
      11.1.19. sql_attr_bigint
      11.1.20. sql_attr_timestamp
      11.1.21. sql_attr_str2ordinal
      11.1.22. sql_attr_float
      11.1.23. sql_attr_multi
      11.1.24. sql_attr_string
      11.1.25. sql_attr_str2wordcount
      11.1.26. sql_column_buffers
      11.1.27. sql_field_string
      11.1.28. sql_field_str2wordcount
      11.1.29. sql_file_field
      11.1.30. sql_query_post
      11.1.31. sql_query_post_index
      11.1.32. sql_ranged_throttle
      11.1.33. sql_query_info
      11.1.34. xmlpipe_command
      11.1.35. xmlpipe_field
      11.1.36. xmlpipe_field_string
      11.1.37. xmlpipe_field_wordcount
      11.1.38. xmlpipe_attr_uint
      11.1.39. xmlpipe_attr_bigint
      11.1.40. xmlpipe_attr_bool
      11.1.41. xmlpipe_attr_timestamp
      11.1.42. xmlpipe_attr_str2ordinal
      11.1.43. xmlpipe_attr_float
      11.1.44. xmlpipe_attr_multi
      11.1.45. xmlpipe_attr_multi_64
      11.1.46. xmlpipe_attr_string
      11.1.47. xmlpipe_fixup_utf8
      11.1.48. mssql_winauth
      11.1.49. mssql_unicode
      11.1.50. unpack_zlib
      11.1.51. unpack_mysqlcompress
      11.1.52. unpack_mysqlcompress_maxsize

   11.2. Index configuration options
      11.2.1. type
      11.2.2. source
      11.2.3. path
      11.2.4. docinfo
      11.2.5. mlock
      11.2.6. morphology
      11.2.7. dict
      11.2.8. index_sp
      11.2.9. index_zones
      11.2.10. min_stemming_len
      11.2.11. stopwords
      11.2.12. wordforms
      11.2.13. exceptions
      11.2.14. min_word_len
      11.2.15. charset_type
      11.2.16. charset_table
      11.2.17. ignore_chars
      11.2.18. min_prefix_len
      11.2.19. min_infix_len
      11.2.20. prefix_fields
      11.2.21. infix_fields
      11.2.22. enable_star
      11.2.23. ngram_len
      11.2.24. ngram_chars
      11.2.25. phrase_boundary
      11.2.26. phrase_boundary_step
      11.2.27. html_strip
      11.2.28. html_index_attrs
      11.2.29. html_remove_elements
      11.2.30. local
      11.2.31. agent
      11.2.32. agent_blackhole
      11.2.33. agent_connect_timeout
      11.2.34. agent_query_timeout
      11.2.35. preopen
      11.2.36. ondisk_dict
      11.2.37. inplace_enable
      11.2.38. inplace_hit_gap
      11.2.39. inplace_docinfo_gap
      11.2.40. inplace_reloc_factor
      11.2.41. inplace_write_factor
      11.2.42. index_exact_words
      11.2.43. overshort_step
      11.2.44. stopword_step
      11.2.45. hitless_words
      11.2.46. expand_keywords
      11.2.47. blend_chars
      11.2.48. blend_mode
      11.2.49. rt_mem_limit
      11.2.50. rt_field
      11.2.51. rt_attr_uint
      11.2.52. rt_attr_bigint
      11.2.53. rt_attr_float
      11.2.54. rt_attr_multi
      11.2.55. rt_attr_multi_64
      11.2.56. rt_attr_timestamp
      11.2.57. rt_attr_string

   11.3. indexer program configuration options
      11.3.1. mem_limit
      11.3.2. max_iops
      11.3.3. max_iosize
      11.3.4. max_xmlpipe2_field
      11.3.5. write_buffer
      11.3.6. max_file_field_buffer
      11.3.7. on_file_field_error

   11.4. searchd program configuration options
      11.4.1. listen
      11.4.2. address
      11.4.3. port
      11.4.4. log
      11.4.5. query_log
      11.4.6. query_log_format
      11.4.7. read_timeout
      11.4.8. client_timeout
      11.4.9. max_children
      11.4.10. pid_file
      11.4.11. max_matches
      11.4.12. seamless_rotate
      11.4.13. preopen_indexes
      11.4.14. unlink_old
      11.4.15. attr_flush_period
      11.4.16. ondisk_dict_default
      11.4.17. max_packet_size
      11.4.18. mva_updates_pool
      11.4.19. crash_log_path
      11.4.20. max_filters
      11.4.21. max_filter_values
      11.4.22. listen_backlog
      11.4.23. read_buffer
      11.4.24. read_unhinted
      11.4.25. max_batch_queries
      11.4.26. subtree_docs_cache
      11.4.27. subtree_hits_cache
      11.4.28. workers
      11.4.29. dist_threads
      11.4.30. binlog_path
      11.4.31. binlog_flush
      11.4.32. binlog_max_log_size
      11.4.33. collation_server
      11.4.34. collation_libc_locale
      11.4.35. plugin_dir
      11.4.36. mysql_version_string
      11.4.37. rt_flush_period
      11.4.38. thread_stack
      11.4.39. expansion_limit
      11.4.40. compat_sphinxql_magics
      11.4.41. watchdog
      11.4.42. prefork_rotation_throttle

A. Sphinx revision history
   A.1. Version 2.0.8-release, 26 apr 2013
   A.2. Version 2.0.7-release, 26 mar 2013
   A.3. Version 2.0.6-release, 22 oct 2012
   A.4. Version 2.0.5-release, 28 jul 2012
   A.5. Version 2.0.4-release, 02 mar 2012
   A.6. Version 2.0.3-release, 23 dec 2011
   A.7. Version 2.0.2-beta, 15 nov 2011
   A.8. Version 2.0.1-beta, 22 apr 2011
   A.9. Version 1.10-beta, 19 jul 2010
   A.10. Version 0.9.9-release, 02 dec 2009
   A.11. Version 0.9.9-rc2, 08 apr 2009
   A.12. Version 0.9.9-rc1, 17 nov 2008
   A.13. Version 0.9.8.1, 30 oct 2008
   A.14. Version 0.9.8, 14 jul 2008
   A.15. Version 0.9.7, 02 apr 2007
   A.16. Version 0.9.7-rc2, 15 dec 2006
   A.17. Version 0.9.7-rc1, 26 oct 2006
   A.18. Version 0.9.6, 24 jul 2006
   A.19. Version 0.9.6-rc1, 26 jun 2006

List of Examples

3.1. Ranged query usage example
3.2. XMLpipe document stream
3.3. xmlpipe2 document stream
3.4. Fully automated live updates
4.1. RT index declaration
5.1. Boolean query example
5.2. Extended matching mode: query example

Chapter 1. Introduction
=======================

Table of Contents

1.1. About
1.2. Sphinx features
1.3. Where to get Sphinx
1.4. License
1.5. Credits
1.6. History

1.1. About
==========

Sphinx is a full-text search engine, publicly distributed under GPL version
2. Commercial licensing (eg. for embedded use) is available upon request.

Technically, Sphinx is a standalone software package provides fast and
relevant full-text search functionality to client applications. It was
specially designed to integrate well with SQL databases storing the data,
and to be easily accessed scripting languages. However, Sphinx does not
depend on nor require any specific database to function.

Applications can access Sphinx search daemon (searchd) using any of the
three different access methods: a) via native search API (SphinxAPI), b)
via Sphinx own implementation of MySQL network protocol (using a small SQL
subset called SphinxQL), or c) via MySQL server with a pluggable storage
engine (SphinxSE).

Official native SphinxAPI implementations for PHP, Perl, Ruby, and Java are
included within the distribution package. API is very lightweight so
porting it to a new language is known to take a few hours or days. Third
party API ports and plugins exist for Perl, C#, Haskell, Ruby-on-Rails, and
possibly other languages and frameworks.

Starting version 1.10-beta, Sphinx supports two different indexing
backends: "disk" index backend, and "realtime" (RT) index backend. Disk
indexes support online full-text index rebuilds, but online updates can
only be done on non-text (attribute) data. RT indexes additionally allow
for online full-text index updates. Previous versions only supported disk
indexes.

Data can be loaded into disk indexes using a so-called data source.
Built-in sources can fetch data directly from MySQL, PostgreSQL, ODBC
compliant database (MS SQL, Oracle, etc), or a pipe in a custom XML format.
Adding new data sources drivers (eg. to natively support other DBMSes) is
designed to be as easy as possible. RT indexes, as of 1.10-beta, can only
be populated using SphinxQL.

As for the name, Sphinx is an acronym which is officially decoded as SQL
Phrase Index. Yes, I know about CMU's Sphinx project.

1.2. Sphinx features
====================

Key Sphinx features are:

   * high indexing and searching performance;
   * advanced indexing and querying tools (flexible and feature-rich text
     tokenizer, querying language, several different ranking modes, etc);
   * advanced result set post-processing (SELECT with expressions, WHERE,
     ORDER BY, GROUP BY etc over text search results);
   * proven scalability up to billions of documents, terabytes of data, and
     thousands of queries per second;
   * easy integration with SQL and XML data sources, and SphinxAPI,
     SphinxQL, or SphinxSE search interfaces;
   * easy scaling with distributed searches.

To expand a bit, Sphinx:

   * has high indexing speed (upto 10-15 MB/sec per core on an internal
     benchmark);
   * has high search speed (upto 150-250 queries/sec per core against
     1,000,000 documents, 1.2 GB of data on an internal benchmark);
   * has high scalability (biggest known cluster indexes over 3,000,000,000
     documents, and busiest one peaks over 50,000,000 queries/day);
   * provides good relevance ranking through combination of phrase
     proximity ranking and statistical (BM25) ranking;
   * provides distributed searching capabilities;
   * provides document excerpts (snippets) generation;
   * provides searching from within application with SphinxAPI or SphinxQL
     interfaces, and from within MySQL with pluggable SphinxSE storage
     engine;
   * supports boolean, phrase, word proximity and other types of queries;
   * supports multiple full-text fields per document (upto 32 by default);
   * supports multiple additional attributes per document (ie. groups,
     timestamps, etc);
   * supports stopwords;
   * supports morphological word forms dictionaries;
   * supports tokenizing exceptions;
   * supports both single-byte encodings and UTF-8;
   * supports stemming (stemmers for English, Russian and Czech are
     built-in; and stemmers for French, Spanish, Portuguese, Italian,
     Romanian, German, Dutch, Swedish, Norwegian, Danish, Finnish,
     Hungarian, are available by building third party libstemmer library);
   * supports MySQL natively (all types of tables, including MyISAM,
     InnoDB, NDB, Archive, etc are supported);
   * supports PostgreSQL natively;
   * supports ODBC compliant databases (MS SQL, Oracle, etc) natively;
   * ...has 50+ other features not listed here, refer to API and
     configuration manual!

1.3. Where to get Sphinx
========================

Sphinx is available through its official Web site at
http://sphinxsearch.com/.

Currently, Sphinx distribution tarball includes the following software:

   * indexer: an utility which creates fulltext indexes;
   * search: a simple command-line (CLI) test utility which searches
     through fulltext indexes;
   * searchd: a daemon which enables external software (eg. Web
     applications) to search through fulltext indexes;
   * sphinxapi: a set of searchd client API libraries for popular Web
     scripting languages (PHP, Python, Perl, Ruby).
   * spelldump: a simple command-line tool to extract the items from an
     ispell or MySpell (as bundled with OpenOffice) format dictionary to
     help customize your index, for use with wordforms.
   * indextool: an utility to dump miscellaneous debug information about
     the index, added in version 0.9.9-rc2.

1.4. License
============

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option)
any later version. See COPYING file for details.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc., 59
Temple Place, Suite 330, Boston, MA 02111-1307 USA

Non-GPL licensing (for OEM/ISV embedded use) can also be arranged, please
contact us to discuss commercial licensing possibilities.

1.5. Credits
============

Author
------

Sphinx initial author (and a benevolent dictator ever since):

   * Andrew Aksyonoff, http://shodan.ru

Team
----

Past and present employees of Sphinx Technologies Inc who should be noted
on their work on Sphinx (in alphabetical order):

   * Alexander Klimenko
   * Alexey Dvoichenkov
   * Alexey Vinogradov
   * Ilya Kuznetsov
   * Stanislav Klinov

Contributors
------------

People who contributed to Sphinx and their contributions (in no particular
order):

   * Robert "coredev" Bengtsson (Sweden), initial version of PostgreSQL
     data source
   * Len Kranendonk, Perl API
   * Dmytro Shteflyuk, Ruby API

Many other people have contributed ideas, bug reports, fixes, etc. Thank
you!

1.6. History
============

Sphinx development was started back in 2001, because I didn't manage to
find an acceptable search solution (for a database driven Web site) which
would meet my requirements. Actually, each and every important aspect was
a problem:

   * search quality (ie. good relevance)

      * statistical ranking methods performed rather bad, especially on
        large collections of small documents (forums, blogs, etc)

   * search speed

      * especially if searching for phrases which contain stopwords, as in
        "to be or not to be"

   * moderate disk and CPU requirements when indexing

      * important in shared hosting enivronment, not to mention the
        indexing speed.

Despite the amount of time passed and numerous improvements made in the
other solutions, there's still no solution which I personally would be
eager to migrate to.

Considering that and a lot of positive feedback received from Sphinx users
during last years, the obvious decision is to continue developing Sphinx
(and, eventually, to take over the world).

Chapter 2. Installation
=======================

Table of Contents

2.1. Supported systems
2.2. Required tools
2.3. Installing Sphinx on Linux
2.4. Installing Sphinx on Windows
2.5. Known installation issues
2.6. Quick Sphinx usage tour

2.1. Supported systems
======================

Most modern UNIX systems with a C++ compiler should be able to compile and
run Sphinx without any modifications.

Currently known systems Sphinx has been successfully running on are:

   * Linux 2.4.x, 2.6.x (many various distributions)
   * Windows 2000, XP, 7
   * FreeBSD 4.x, 5.x, 6.x, 7.x, 8.x
   * NetBSD 1.6, 3.0
   * Solaris 9, 11
   * Mac OS X

CPU architectures known to work include i386 (aka x86), amd64 (aka x86_64),
SPARC64, and ARM.

Chances are good that Sphinx should work on other Unix platforms and/or CPU
architectures just as well. Please report any other platforms that worked
for you!

All platforms are production quality. There are no principal functional
limitations on any platform.

2.2. Required tools
===================

On UNIX, you will need the following tools to build and install Sphinx:

   * a working C++ compiler. GNU gcc is known to work.
   * a good make program. GNU make is known to work.

On Windows, you will need Microsoft Visual C/C++ Studio .NET 2005 or above.
Other compilers/environments will probably work as well, but for the time
being, you will have to build makefile (or other environment specific
project files) manually.

2.3. Installing Sphinx on Linux
===============================

   1. Extract everything from the distribution tarball (haven't you
      already?) and go to the sphinx subdirectory. (We are using version
      2.0.1-beta here for the sake of example only; be sure to change this
      to a specific version you're using.)

      | $ tar xzvf sphinx-2.0.1-beta.tar.gz
      | $ cd sphinx

   2. Run the configuration program:

      | $ ./configure

      There's a number of options to configure. The complete listing may be
      obtained by using --help switch. The most important ones are:

      * --prefix, which specifies where to install Sphinx; such as
        --prefix=/usr/local/sphinx (all of the examples use this prefix)
      * --with-mysql, which specifies where to look for MySQL include and
        library files, if auto-detection fails;
      * --with-pgsql, which specifies where to look for PostgreSQL include
        and library files.

   3. Build the binaries:

      | $ make

   4. Install the binaries in the directory of your choice: (defaults to
      /usr/local/bin/ on *nix systems, but is overridden with configure
      --prefix)

      | $ make install

2.4. Installing Sphinx on Windows
=================================

Installing Sphinx on a Windows server is often easier than installing on
a Linux environment; unless you are preparing code patches, you can use the
pre-compiled binary files from the Downloads area on the website.

   1. Extract everything from the .zip file you have downloaded -
      sphinx-2.0.1-beta-win32.zip, or sphinx-2.0.1-beta-win32-pgsql.zip if
      you need PostgresSQL support as well. (We are using version
      2.0.1-beta here for the sake of example only; be sure to change this
      to a specific version you're using.) You can use Windows Explorer in
      Windows XP and up to extract the files, or a freeware package like
      7Zip to open the archive.

      For the remainder of this guide, we will assume that the folders are
      unzipped into C:\Sphinx, such that searchd.exe can be found in
      C:\Sphinx\bin\searchd.exe. If you decide to use any different
      location for the folders or configuration file, please change it
      accordingly.

   2. Edit the contents of sphinx.conf.in - specifically entries relating
      to @CONFDIR@ - to paths suitable for your system.
   3. Install the searchd system as a Windows service:

      C:\Sphinx\bin> C:\Sphinx\bin\searchd --install --config
      C:\Sphinx\sphinx.conf.in --servicename SphinxSearch

   4. The searchd service will now be listed in the Services panel within
      the Management Console, available from Administrative Tools. It will
      not have been started, as you will need to configure it and build
      your indexes with indexer before starting the service. A guide to do
      this can be found under Quick tour.

      During the next steps of the install (which involve running indexer
      pretty much as you would on Linux) you may find that you get an error
      relating to libmysql.dll not being found. If you have MySQL
      installed, you should find a copy of this library in your Windows
      directory, or sometimes in Windows\System32, or failing that in the
      MySQL core directories. If you do receive an error please copy
      libmysql.dll into the bin directory.

2.5. Known installation issues
==============================

If configure fails to locate MySQL headers and/or libraries, try checking
for and installing mysql-devel package. On some systems, it is not
installed by default.

If make fails with a message which look like

   | /bin/sh: g++: command not found
   | make[1]: *** [libsphinx_a-sphinx.o] Error 127

try checking for and installing gcc-c++ package.

If you are getting compile-time errors which look like

   | sphinx.cpp:67: error: invalid application of `sizeof' to
   |     incomplete type `Private::SizeError<false>'

this means that some compile-time type size check failed. The most probable
reason is that off_t type is less than 64-bit on your system. As a quick
hack, you can edit sphinx.h and replace off_t with DWORD in a typedef for
SphOffset_t, but note that this will prohibit you from using full-text
indexes larger than 2 GB. Even if the hack helps, please report such
issues, providing the exact error message and compiler/OS details, so
I could properly fix them in next releases.

If you keep getting any other error, or the suggestions above do not seem
to help you, please don't hesitate to contact me.

2.6. Quick Sphinx usage tour
============================

All the example commands below assume that you installed Sphinx in
/usr/local/sphinx, so searchd can be found in
/usr/local/sphinx/bin/searchd.

To use Sphinx, you will need to:

   1. Create a configuration file.

      Default configuration file name is sphinx.conf. All Sphinx programs
      look for this file in current working directory by default.

      Sample configuration file, sphinx.conf.dist, which has all the
      options documented, is created by configure. Copy and edit that
      sample file to make your own configuration: (assuming Sphinx is
      installed into /usr/local/sphinx/)

      | $ cd /usr/local/sphinx/etc
      | $ cp sphinx.conf.dist sphinx.conf
      | $ vi sphinx.conf

      Sample configuration file is setup to index documents table from
      MySQL database test; so there's example.sql sample data file to
      populate that table with a few documents for testing purposes:

      | $ mysql -u test < /usr/local/sphinx/etc/example.sql

   2. Run the indexer to create full-text index from your data:

      | $ cd /usr/local/sphinx/etc
      | $ /usr/local/sphinx/bin/indexer --all

   3. Query your newly created index!

To query the index from command line, use search utility:

   | $ cd /usr/local/sphinx/etc
   | $ /usr/local/sphinx/bin/search test

To query the index from your PHP scripts, you need to:

   1. Run the search daemon which your script will talk to:

      | $ cd /usr/local/sphinx/etc
      | $ /usr/local/sphinx/bin/searchd

   2. Run the attached PHP API test script (to ensure that the daemon was
      succesfully started and is ready to serve the queries):

      | $ cd sphinx/api
      | $ php test.php test

   3. Include the API (it's located in api/sphinxapi.php) into your own
      scripts and use it.

Happy searching!

Chapter 3. Indexing
===================

Table of Contents

3.1. Data sources
3.2. Full-text fields
3.3. Attributes
3.4. MVA (multi-valued attributes)
3.5. Indexes
3.6. Restrictions on the source data
3.7. Charsets, case folding, and translation tables
3.8. SQL data sources (MySQL, PostgreSQL)
3.9. xmlpipe data source
3.10. xmlpipe2 data source
3.11. Live index updates
3.12. Delta index updates
3.13. Index merging

3.1. Data sources
=================

The data to be indexed can generally come from very different sources: SQL
databases, plain text files, HTML files, mailboxes, and so on. From Sphinx
point of view, the data it indexes is a set of structured documents, each
of which has the same set of fields and attributes. This is similar to SQL,
where each row would correspond to a document, and each column to either
a field or an attribute.

Depending on what source Sphinx should get the data from, different code is
required to fetch the data and prepare it for indexing. This code is called
data source driver (or simply driver or data source for brevity).

At the time of this writing, there are built-in drivers for MySQL,
PostgreSQL, MS SQL (on Windows), and ODBC. There is also a generic driver
called xmlpipe, which runs a specified command and reads the data from its
stdout. See Section 3.9, <<xmlpipe data source>> section for the format
description.

There can be as many sources per index as necessary. They will be
sequentially processed in the very same order which was specifed in index
definition. All the documents coming from those sources will be merged as
if they were coming from a single source.

3.2. Full-text fields
=====================

Full-text fields (or just fields for brevity) are the textual document
contents that get indexed by Sphinx, and can be (quickly) searched for
keywords.

Fields are named, and you can limit your searches to a single field (eg.
search through "title" only) or a subset of fields (eg. to "title" and
"abstract" only). Sphinx index format generally supports up to 256 fields.
However, up to version 2.0.1-beta indexes were forcibly limited by 32
fields, because of certain complications in the matching engine. Full
support for up to 256 fields was added in version 2.0.2-beta.

Note that the original contents of the fields are not stored in the Sphinx
index. The text that you send to Sphinx gets processed, and a full-text
index (a special data structure that enables quick searches for a keyword)
gets built from that text. But the original text contents are then simply
discarded. Sphinx assumes that you store those contents elsewhere anyway.

Moreover, it is impossible to fully reconstruct the original text, because
the specific whitespace, capitalization, punctuation, etc will all be lost
during indexing. It is theoretically possible to partially reconstruct
a given document from the Sphinx full-text index, but that would be a slow
process (especially if the CRC dictionary is used, which does not even
store the original keywords and works with their hashes instead).

3.3. Attributes
===============

Attributes are additional values associated with each document that can be
used to perform additional filtering and sorting during search.

It is often desired to additionally process full-text search results based
not only on matching document ID and its rank, but on a number of other
per-document values as well. For instance, one might need to sort news
search results by date and then relevance, or search through products
within specified price range, or limit blog search to posts made by
selected users, or group results by month. To do that efficiently, Sphinx
allows to attach a number of additional attributes to each document, and
store their values in the full-text index. It's then possible to use stored
values to filter, sort, or group full-text matches.

Attributes, unlike the fields, are not full-text indexed. They are stored
in the index, but it is not possible to search them as full-text, and
attempting to do so results in an error.

For example, it is impossible to use the extended matching mode expression
@column 1 to match documents where column is 1, if column is an attribute,
and this is still true even if the numeric digits are normally indexed.

Attributes can be used for filtering, though, to restrict returned rows, as
well as sorting or result grouping; it is entirely possible to sort results
purely based on attributes, and ignore the search relevance tools.
Additionally, attributes are returned from the search daemon, while the
indexed text is not.

A good example for attributes would be a forum posts table. Assume that
only title and content fields need to be full-text searchable - but that
sometimes it is also required to limit search to a certain author or
a sub-forum (ie. search only those rows that have some specific values of
author_id or forum_id columns in the SQL table); or to sort matches by
post_date column; or to group matching posts by month of the post_date and
calculate per-group match counts.

This can be achieved by specifying all the mentioned columns (excluding
title and content, that are full-text fields) as attributes, indexing them,
and then using API calls to setup filtering, sorting, and grouping. Here as
an example.

Example sphinx.conf part:
-------------------------

   | ...
   | sql_query = SELECT id, title, content, \
   | 	author_id, forum_id, post_date FROM my_forum_posts
   | sql_attr_uint = author_id
   | sql_attr_uint = forum_id
   | sql_attr_timestamp = post_date
   | ...

Example application code (in PHP):
----------------------------------

   | // only search posts by author whose ID is 123
   | $cl->SetFilter ( "author_id", array ( 123 ) );
   | 
   | // only search posts in sub-forums 1, 3 and 7
   | $cl->SetFilter ( "forum_id", array ( 1,3,7 ) );
   | 
   | // sort found posts by posting date in descending order
   | $cl->SetSortMode ( SPH_SORT_ATTR_DESC, "post_date" );

Attributes are named. Attribute names are case insensitive. Attributes are
not full-text indexed; they are stored in the index as is. Currently
supported attribute types are:

   * unsigned integers (1-bit to 32-bit wide);
   * UNIX timestamps;
   * floating point values (32-bit, IEEE 754 single precision);
   * string ordinals (specially computed integers);
   * strings (since 1.10-beta);
   * MVA, multi-value attributes (variable-length lists of 32-bit unsigned
     integers).

The complete set of per-document attribute values is sometimes referred to
as docinfo. Docinfos can either be

   * stored separately from the main full-text index data ("extern"
     storage, in .spa file), or
   * attached to each occurence of document ID in full-text index data
     ("inline" storage, in .spd file).

When using extern storage, a copy of .spa file (with all the attribute
values for all the documents) is kept in RAM by searchd at all times. This
is for performance reasons; random disk I/O would be too slow. On the
contrary, inline storage does not require any additional RAM at all, but
that comes at the cost of greatly inflating the index size: remember that
it copies all attribute value every time when the document ID is mentioned,
and that is exactly as many times as there are different keywords in the
document. Inline may be the only viable option if you have only a few
attributes and need to work with big datasets in limited RAM. However, in
most cases extern storage makes both indexing and searching much more
efficient.

Search-time memory requirements for extern storage are
(1+number_of_attrs)*number_of_docs*4 bytes, ie. 10 million docs with
2 groups and 1 timestamp will take (1+2+1)*10M*4 = 160 MB of RAM. This is
PER DAEMON, not per query. searchd will allocate 160 MB on startup, read
the data and keep it shared between queries. The children will NOT allocate
any additional copies of this data.

3.4. MVA (multi-valued attributes)
==================================

MVAs, or multi-valued attributes, are an important special type of
per-document attributes in Sphinx. MVAs let you attach sets of numeric
values to every document. That is useful to implement article tags, product
categories, etc. Filtering and group-by (but not sorting) on MVA attributes
is supported.

As of version 2.0.2-beta, MVA values can either be unsigned 32-bit integers
(UNSIGNED INTEGER) or signed 64-bit integers (BIGINT). Up to version
2.0.1-beta, only the unsigned 32-bit values were supported.

The set size is not limited, you can have an arbitrary number of values
attached to each document as long as RAM permits (.spm file that contains
the MVA values will be precached in RAM by searchd). The source data can be
taken either from a separate query, or from a document field; see source
type in sql_attr_multi. In the first case the query will have to return
pairs of document ID and MVA values, in the second one the field will be
parsed for integer values. There are absolutely no requirements as to
incoming data order; the values will be automatically grouped by document
ID (and internally sorted within the same ID) during indexing anyway.

When filtering, a document will match the filter on MVA attribute if any of
the values satisfy the filtering condition. (Therefore, documents that pass
through exclude filters will not contain any of the forbidden values.) When
grouping by MVA attribute, a document will contribute to as many groups as
there are different MVA values associated with that document. For instance,
if the collection contains exactly 1 document having a 'tag' MVA with
values 5, 7, and 11, grouping on 'tag' will produce 3 groups with '@count'
equal to 1 and '@groupby' key values of 5, 7, and 11 respectively. Also
note that grouping by MVA might lead to duplicate documents in the result
set: because each document can participate in many groups, it can be chosen
as the best one in in more than one group, leading to duplicate IDs. PHP
API historically uses ordered hash on the document ID for the resulting
rows; so you'll also need to use SetArrayResult() in order to employ
group-by on MVA with PHP API.

3.5. Indexes
============

To be able to answer full-text search queries fast, Sphinx needs to build
a special data structure optimized for such queries from your text data.
This structure is called index; and the process of building index from text
is called indexing.

Different index types are well suited for different tasks. For example,
a disk-based tree-based index would be easy to update (ie. insert new
documents to existing index), but rather slow to search. Therefore, Sphinx
architecture allows for different index types to be implemented easily.

The only index type which is implemented in Sphinx at the moment is
designed for maximum indexing and searching speed. This comes at a cost of
updates being really slow; theoretically, it might be slower to update this
type of index than than to reindex it from scratch. However, this very
frequently could be worked around with muiltiple indexes, see Section 3.11,
<<Live index updates>> for details.

It is planned to implement more index types, including the type which would
be updateable in real time.

There can be as many indexes per configuration file as necessary. indexer
utility can reindex either all of them (if --all option is specified), or
a certain explicitly specified subset. searchd utility will serve all the
specified indexes, and the clients can specify what indexes to search in
run time.

3.6. Restrictions on the source data
====================================

There are a few different restrictions imposed on the source data which is
going to be indexed by Sphinx, of which the single most important one is:

ALL DOCUMENT IDS MUST BE UNIQUE UNSIGNED NON-ZERO INTEGER NUMBERS (32-BIT
OR 64-BIT, DEPENDING ON BUILD TIME SETTINGS).

If this requirement is not met, different bad things can happen. For
instance, Sphinx can crash with an internal assertion while indexing; or
produce strange results when searching due to conflicting IDs. Also,
a 1000-pound gorilla might eventually come out of your display and start
throwing barrels at you. You've been warned.

3.7. Charsets, case folding, and translation tables
===================================================

When indexing some index, Sphinx fetches documents from the specified
sources, splits the text into words, and does case folding so that "Abc",
"ABC" and "abc" would be treated as the same word (or, to be pedantic,
term).

To do that properly, Sphinx needs to know

   * what encoding is the source text in;
   * what characters are letters and what are not;
   * what letters should be folded to what letters.

This should be configured on a per-index basis using charset_type and
charset_table options. charset_type specifies whether the document encoding
is single-byte (SBCS) or UTF-8. charset_table specifies the table that maps
letter characters to their case folded versions. The characters that are
not in the table are considered to be non-letters and will be treated as
word separators when indexing or searching through this index.

Note that while default tables do not include space character (ASCII code
0x20, Unicode U+0020) as a letter, it's in fact perfectly legal to do so.
This can be useful, for instance, for indexing tag clouds, so that
space-separated word sets would index as a single search query term.

Default tables currently include English and Russian characters. Please do
submit your tables for other languages!

3.8. SQL data sources (MySQL, PostgreSQL)
=========================================

With all the SQL drivers, indexing generally works as follows.

   * connection to the database is established;
   * pre-query (see Section 11.1.11, <<sql_query_pre>>) is executed to
     perform any necessary initial setup, such as setting per-connection
     encoding with MySQL;
   * main query (see Section 11.1.12, <<sql_query>>) is executed and the
     rows it returns are indexed;
   * post-query (see Section 11.1.30, <<sql_query_post>>) is executed to
     perform any necessary cleanup;
   * connection to the database is closed;
   * indexer does the sorting phase (to be pedantic, index-type specific
     post-processing);
   * connection to the database is established again;
   * post-index query (see Section 11.1.31, <<sql_query_post_index>>) is
     executed to perform any necessary final cleanup;
   * connection to the database is closed again.

Most options, such as database user/host/password, are straightforward.
However, there are a few subtle things, which are discussed in more detail
here.

Ranged queries
--------------

Main query, which needs to fetch all the documents, can impose a read lock
on the whole table and stall the concurrent queries (eg. INSERTs to MyISAM
table), waste a lot of memory for result set, etc. To avoid this, Sphinx
supports so-called ranged queries. With ranged queries, Sphinx first
fetches min and max document IDs from the table, and then substitutes
different ID intervals into main query text and runs the modified query to
fetch another chunk of documents. Here's an example.

Example 3.1. Ranged query usage example

   | # in sphinx.conf
   | 
   | sql_query_range	= SELECT MIN(id),MAX(id) FROM documents
   | sql_range_step = 1000
   | sql_query = SELECT * FROM documents WHERE id>=$start AND id<=$end

If the table contains document IDs from 1 to, say, 2345, then sql_query
would be run three times:

   1. with $start replaced with 1 and $end replaced with 1000;
   2. with $start replaced with 1001 and $end replaced with 2000;
   3. with $start replaced with 2001 and $end replaced with 2345.

Obviously, that's not much of a difference for 2000-row table, but when it
comes to indexing 10-million-row MyISAM table, ranged queries might be of
some help.

sql_post vs. sql_post_index
---------------------------

The difference between post-query and post-index query is in that
post-query is run immediately when Sphinx received all the documents, but
further indexing may still fail for some other reason. On the contrary, by
the time the post-index query gets executed, it is guaranteed that the
indexing was succesful. Database connection is dropped and re-established
because sorting phase can be very lengthy and would just timeout otherwise.

3.9. xmlpipe data source
========================

xmlpipe data source was designed to enable users to plug data into Sphinx
without having to implement new data sources drivers themselves. It is
limited to 2 fixed fields and 2 fixed attributes, and is deprecated in
favor of Section 3.10, <<xmlpipe2 data source>> now. For new streams, use
xmlpipe2.

To use xmlpipe, configure the data source in your configuration file as
follows:

   | source example_xmlpipe_source
   | {
   |     type = xmlpipe
   |     xmlpipe_command = perl /www/mysite.com/bin/sphinxpipe.pl
   | }

The indexer will run the command specified in xmlpipe_command, and then
read, parse and index the data it prints to stdout. More formally, it opens
a pipe to given command and then reads from that pipe.

indexer will expect one or more documents in custom XML format. Here's the
example document stream, consisting of two documents:

Example 3.2. XMLpipe document stream

   | <document>
   | <id>123</id>
   | <group>45</group>
   | <timestamp>1132223498</timestamp>
   | <title>test title</title>
   | <body>
   | this is my document body
   | </body>
   | </document>
   | 
   | <document>
   | <id>124</id>
   | <group>46</group>
   | <timestamp>1132223498</timestamp>
   | <title>another test</title>
   | <body>
   | this is another document
   | </body>
   | </document>

Legacy xmlpipe legacy driver uses a builtin parser which is pretty fast but
really strict and does not actually fully support XML. It requires that all
the fields must be present, formatted exactly as in this example, and occur
exactly in the same order. The only optional field is timestamp; it
defaults to 1.

3.10. xmlpipe2 data source
==========================

xmlpipe2 lets you pass arbitrary full-text and attribute data to Sphinx in
yet another custom XML format. It also allows to specify the schema (ie.
the set of fields and attributes) either in the XML stream itself, or in
the source settings.

When indexing xmlpipe2 source, indexer runs the given command, opens a pipe
to its stdout, and expects well-formed XML stream. Here's sample stream
data:

Example 3.3. xmlpipe2 document stream

   | <?xml version="1.0" encoding="utf-8"?>
   | <sphinx:docset>
   | 
   | <sphinx:schema>
   | <sphinx:field name="subject"/> 
   | <sphinx:field name="content"/>
   | <sphinx:attr name="published" type="timestamp"/>
   | <sphinx:attr name="author_id" type="int" bits="16" default="1"/>
   | </sphinx:schema>
   | 
   | <sphinx:document id="1234">
   | <content>this is the main content <![CDATA[[and this <cdata> entry
   | must be handled properly by xml parser lib]]></content>
   | <published>1012325463</published>
   | <subject>note how field/attr tags can be
   | in <b class="red">randomized</b> order</subject>
   | <misc>some undeclared element</misc>
   | </sphinx:document>
   | 
   | <sphinx:document id="1235">
   | <subject>another subject</subject>
   | <content>here comes another document, and i am given to understand,
   | that in-document field order must not matter, sir</content>
   | <published>1012325467</published>
   | </sphinx:document>
   | 
   | <!-- ... even more sphinx:document entries here ... -->
   | 
   | <sphinx:killlist>
   | <id>1234</id>
   | <id>4567</id>
   | </sphinx:killlist>
   | 
   | </sphinx:docset>

Arbitrary fields and attributes are allowed. They also can occur in the
stream in arbitrary order within each document; the order is ignored. There
is a restriction on maximum field length; fields longer than 2 MB will be
truncated to 2 MB (this limit can be changed in the source).

The schema, ie. complete fields and attributes list, must be declared
before any document could be parsed. This can be done either in the
configuration file using xmlpipe_field and xmlpipe_attr_XXX settings, or
right in the stream using <sphinx:schema> element. <sphinx:schema> is
optional. It is only allowed to occur as the very first sub-element in
<sphinx:docset>. If there is no in-stream schema definition, settings from
the configuration file will be used. Otherwise, stream settings take
precedence.

Unknown tags (which were not declared neither as fields nor as attributes)
will be ignored with a warning. In the example above, <misc> will be
ignored. All embedded tags and their attributes (such as <b> in <subject>
in the example above) will be silently ignored.

Support for incoming stream encodings depends on whether iconv is installed
on the system. xmlpipe2 is parsed using libexpat parser that understands
US-ASCII, ISO-8859-1, UTF-8 and a few UTF-16 variants natively. Sphinx
configure script will also check for libiconv presence, and utilize it to
handle other encodings. libexpat also enforces the requirement to use UTF-8
charset on Sphinx side, because the parsed data it returns is always in
UTF-8.

XML elements (tags) recognized by xmlpipe2 (and their attributes where
applicable) are:

sphinx:docset
   Mandatory top-level element, denotes and contains xmlpipe2 document set.

sphinx:schema
   Optional element, must either occur as the very first child of
   sphinx:docset, or never occur at all. Declares the document schema.
   Contains field and attribute declarations. If present, overrides
   per-source settings from the configuration file.

sphinx:field
   Optional element, child of sphinx:schema. Declares a full-text field.
   Known attributes are:

      * "name", specifies the XML element name that will be treated as
        a full-text field in the subsequent documents.
      * "attr", specifies whether to also index this field as a string or
        word count attribute. Possible values are "string" and "wordcount".
        Introduced in version 1.10-beta.

sphinx:attr
   Optional element, child of sphinx:schema. Declares an attribute. Known
   attributes are:

      * "name", specifies the element name that should be treated as an
        attribute in the subsequent documents.
      * "type", specifies the attribute type. Possible values are "int",
        "timestamp", "str2ordinal", "bool", "float" and "multi".
      * "bits", specifies the bit size for "int" attribute type. Valid
        values are 1 to 32.
      * "default", specifies the default value for this attribute that
        should be used if the attribute's element is not present in the
        document.

sphinx:document
   Mandatory element, must be a child of sphinx:docset. Contains arbitrary
   other elements with field and attribute values to be indexed, as
   declared either using sphinx:field and sphinx:attr elements or in the
   configuration file. The only known attribute is "id" that must contain
   the unique integer document ID.

sphinx:killlist
   Optional element, child of sphinx:docset. Contains a number of "id"
   elements whose contents are document IDs to be put into a kill-list for
   this index.

3.11. Live index updates
========================

There are two major approaches to maintaining the full-text index contents
up to date. Note, however, that both these approaches deal with the task of
full-text data updates, and not attribute updates. Instant attribute
updates are supported since version 0.9.8. Refer to UpdateAttributes() API
call description for details.

First, you can use disk-based indexes, partition them manually, and only
rebuild the smaller partitions (so-called "deltas") frequently. By
minimizing the rebuild size, you can reduce the average indexing lag to
something as low as 30-60 seconds. This approach was the the only one
available in versions 0.9.x. On huge collections it actually might be the
most efficient one. Refer to Section 3.12, <<Delta index updates>> for
details.

Second, versions 1.x (starting with 1.10-beta) add support for so-called
real-time indexes (RT indexes for short) that on-the-fly updates of the
full-text data. Updates on a RT index can appear in the search results in
1-2 milliseconds, ie. 0.001-0.002 seconds. However, RT index are less
efficient for bulk indexing huge amounts of data. Refer to Chapter 4,
Real-time indexes for details.

3.12. Delta index updates
=========================

There's a frequent situation when the total dataset is too big to be
reindexed from scratch often, but the amount of new records is rather
small. Example: a forum with a 1,000,000 archived posts, but only 1,000 new
posts per day.

In this case, "live" (almost real time) index updates could be implemented
using so called "main+delta" scheme.

The idea is to set up two sources and two indexes, with one "main" index
for the data which only changes rarely (if ever), and one "delta" for the
new documents. In the example above, 1,000,000 archived posts would go to
the main index, and newly inserted 1,000 posts/day would go to the delta
index. Delta index could then be reindexed very frequently, and the
documents can be made available to search in a matter of minutes.

Specifying which documents should go to what index and reindexing main
index could also be made fully automatic. One option would be to make
a counter table which would track the ID which would split the documents,
and update it whenever the main index is reindexed.

Example 3.4. Fully automated live updates

   | # in MySQL
   | CREATE TABLE sph_counter
   | (
   |     counter_id INTEGER PRIMARY KEY NOT NULL,
   |     max_doc_id INTEGER NOT NULL
   | );
   | 
   | # in sphinx.conf
   | source main
   | {
   |     # ...
   |     sql_query_pre = SET NAMES utf8
   |     sql_query_pre = REPLACE INTO sph_counter SELECT 1, MAX(id) FROM documents
   |     sql_query = SELECT id, title, body FROM documents \
   |         WHERE id<=( SELECT max_doc_id FROM sph_counter WHERE counter_id=1 )
   | }
   | 
   | source delta : main
   | {
   |     sql_query_pre = SET NAMES utf8
   |     sql_query = SELECT id, title, body FROM documents \
   |         WHERE id>( SELECT max_doc_id FROM sph_counter WHERE counter_id=1 )
   | }
   | 
   | index main
   | {
   |     source = main
   |     path = /path/to/main
   |     # ... all the other settings
   | }
   | 
   | # note how all other settings are copied from main,
   | # but source and path are overridden (they MUST be)
   | index delta : main
   | {
   |     source = delta
   |     path = /path/to/delta
   | }

Note how we're overriding sql_query_pre in the delta source. We need to
explicitly have that override. Otherwise REPLACE query would be run when
indexing delta source too, effectively nullifying it. However, when we
issue the directive in the inherited source for the first time, it removes
all inherited values, so the encoding setup is also lost. So sql_query_pre
in the delta can not just be empty; and we need to issue the encoding setup
query explicitly once again.

3.13. Index merging
===================

Merging two existing indexes can be more efficient that indexing the data
from scratch, and desired in some cases (such as merging 'main' and 'delta'
indexes instead of simply reindexing 'main' in 'main+delta' partitioning
scheme). So indexer has an option to do that. Merging the indexes is
normally faster than reindexing but still not instant on huge indexes.
Basically, it will need to read the contents of both indexes once and write
the result once. Merging 100 GB and 1 GB index, for example, will result in
202 GB of IO (but that's still likely less than the indexing from scratch
requires).

The basic command syntax is as follows:

   | indexer --merge DSTINDEX SRCINDEX [--rotate]

Only the DSTINDEX index will be affected: the contents of SRCINDEX will be
merged into it. --rotate switch will be required if DSTINDEX is already
being served by searchd. The initially devised usage pattern is to merge
a smaller update from SRCINDEX into DSTINDEX. Thus, when merging the
attributes, values from SRCINDEX will win if duplicate document IDs are
encountered. Note, however, that the "old" keywords will not be
automatically removed in such cases. For example, if there's a keyword
"old" associated with document 123 in DSTINDEX, and a keyword "new"
associated with it in SRCINDEX, document 123 will be found by both keywords
after the merge. You can supply an explicit condition to remove documents
from DSTINDEX to mitigate that; the relevant switch is --merge-dst-range:

   | indexer --merge main delta --merge-dst-range deleted 0 0

This switch lets you apply filters to the destination index along with
merging. There can be several filters; all of their conditions must be met
in order to include the document in the resulting mergid index. In the
example above, the filter passes only those records where 'deleted' is 0,
eliminating all records that were flagged as deleted (for instance, using
UpdateAttributes() call).

Chapter 4. Real-time indexes
============================

Table of Contents

4.1. RT indexes overview
4.2. Known caveats with RT indexes
4.3. RT index internals
4.4. Binary logging

Real-time indexes (or RT indexes for brevity) are a new backend that lets
you insert, update, or delete documents (rows) on the fly. RT indexes were
added in version 1.10-beta. While querying of RT indexes is possible using
any of the SphinxAPI, SphinxQL, or SphinxSE, updating them is only possible
via SphinxQL at the moment. Full SphinxQL reference is available in
Chapter 7, SphinxQL reference.

4.1. RT indexes overview
========================

RT indexes should be declared in sphinx.conf, just as every other index
type. Notable differences from the regular, disk-based indexes are that a)
data sources are not required and ignored, and b) you should explicitly
enumerate all the text fields, not just attributes. Here's an example:

Example 4.1. RT index declaration

   | index rt
   | {
   | 	type = rt
   | 	path = /usr/local/sphinx/data/rt
   | 	rt_field = title
   | 	rt_field = content
   | 	rt_attr_uint = gid
   | }

As of 2.0.1-beta and above, RT indexes are production quality, despite
a few missing features.

RT index can be accessed using MySQL protocol. INSERT, REPLACE, DELETE, and
SELECT statements against RT index are supported. For instance, this is an
example session with the sample index above:

   | $ mysql -h 127.0.0.1 -P 9306
   | Welcome to the MySQL monitor.  Commands end with ; or \g.
   | Your MySQL connection id is 1
   | Server version: 1.10-dev (r2153)
   | 
   | Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
   | 
   | mysql> INSERT INTO rt VALUES ( 1, 'first record', 'test one', 123 );
   | Query OK, 1 row affected (0.05 sec)
   | 
   | mysql> INSERT INTO rt VALUES ( 2, 'second record', 'test two', 234 );
   | Query OK, 1 row affected (0.00 sec)
   | 
   | mysql> SELECT * FROM rt;
   | +------+--------+------+
   | | id   | weight | gid  |
   | +------+--------+------+
   | |    1 |      1 |  123 |
   | |    2 |      1 |  234 |
   | +------+--------+------+
   | 2 rows in set (0.02 sec)
   | 
   | mysql> SELECT * FROM rt WHERE MATCH('test');
   | +------+--------+------+
   | | id   | weight | gid  |
   | +------+--------+------+
   | |    1 |   1643 |  123 |
   | |    2 |   1643 |  234 |
   | +------+--------+------+
   | 2 rows in set (0.01 sec)
   | 
   | mysql> SELECT * FROM rt WHERE MATCH('@title test');
   | Empty set (0.00 sec)

Both partial and batch INSERT syntaxes are supported, ie. you can specify
a subset of columns, and insert several rows at a time. Deletions are also
possible using DELETE statement; the only currently supported syntax is
DELETE FROM <index> WHERE id=<id>. REPLACE is also supported, enabling you
to implement updates.

   | mysql> INSERT INTO rt ( id, title ) VALUES ( 3, 'third row' ), ( 4, 'fourth entry' );
   | Query OK, 2 rows affected (0.01 sec)
   | 
   | mysql> SELECT * FROM rt;
   | +------+--------+------+
   | | id   | weight | gid  |
   | +------+--------+------+
   | |    1 |      1 |  123 |
   | |    2 |      1 |  234 |
   | |    3 |      1 |    0 |
   | |    4 |      1 |    0 |
   | +------+--------+------+
   | 4 rows in set (0.00 sec)
   | 
   | mysql> DELETE FROM rt WHERE id=2;
   | Query OK, 0 rows affected (0.00 sec)
   | 
   | mysql> SELECT * FROM rt WHERE MATCH('test');
   | +------+--------+------+
   | | id   | weight | gid  |
   | +------+--------+------+
   | |    1 |   1500 |  123 |
   | +------+--------+------+
   | 1 row in set (0.00 sec)
   | 
   | mysql> INSERT INTO rt VALUES ( 1, 'first record on steroids', 'test one', 123 );
   | ERROR 1064 (42000): duplicate id '1'
   | 
   | mysql> REPLACE INTO rt VALUES ( 1, 'first record on steroids', 'test one', 123 );
   | Query OK, 1 row affected (0.01 sec)
   | 
   | mysql> SELECT * FROM rt WHERE MATCH('steroids');
   | +------+--------+------+
   | | id   | weight | gid  |
   | +------+--------+------+
   | |    1 |   1500 |  123 |
   | +------+--------+------+
   | 1 row in set (0.01 sec)

Data stored in RT index should survive clean shutdown. When binary logging
is enabled, it should also survive crash and/or dirty shutdown, and recover
on subsequent startup.

4.2. Known caveats with RT indexes
==================================

RT indexes are currently quality feature, but there are still a few known
usage quirks. Those quirks are listed in this section.

   * Prefix indexing is supported with dict = keywords starting 2.0.2-beta.
     Infix indexing is experimental in trunk.
   * Disk chunks optimization routine is not implemented yet.
   * On initial index creation, attributes are reordered by type, in the
     following order: uint, bigint, float, timestamp, string. So when using
     INSERT without an explicit column names list, specify all uint column
     values first, then bigint, etc.
   * Default conservative RAM chunk limit (rt_mem_limit) of 32M can lead to
     poor performance on bigger indexes, you should raise it to 256..1024M
     if you're planning to index gigabytes.
   * High DELETE/REPLACE rate can lead to kill-list fragmentation and
     impact searching performance.
   * No transaction size limits are currently imposed; too many concurrent
     INSERT/REPLACE transactions might therefore consume a lot of RAM.
   * In case of a damaged binlog, recovery will stop on the first damaged
     transaction, even though it's technically possible to keep looking
     further for subsequent undamaged transactions, and recover those. This
     mid-file damage case (due to flaky HDD/CDD/tape?) is supposed to be
     extremely rare, though.
   * Multiple INSERTs grouped in a single transaction perform better than
     equivalent single-row transactions and are recommended for batch
     loading of data.

4.3. RT index internals
=======================

RT index is internally chunked. It keeps a so-called RAM chunk that stores
all the most recent changes. RAM chunk memory usage is rather strictly
limited with per-index rt_mem_limit directive. Once RAM chunk grows over
this limit, a new disk chunk is created from its data, and RAM chunk is
reset. Thus, while most changes on the RT index will be performed in RAM
only and complete instantly (in milliseconds), those changes that overflow
the RAM chunk will stall for the duration of disk chunk creation (a few
seconds).

Disk chunks are, in fact, just regular disk-based indexes. But they're
a part of an RT index and automatically managed by it, so you need not
configure nor manage them manually. Because a new disk chunk is created
every time RT chunk overflows the limit, and because in-memory chunk format
is close to on-disk format, the disk chunks will be approximately
rt_mem_limit bytes in size each.

Generally, it is better to set the limit bigger, to minimize both the
frequency of flushes, and the index fragmentation (number of disk chunks).
For instance, on a dedicated search server that handles a big RT index, it
can be advised to set rt_mem_limit to 1-2 GB. A global limit on all indexes
is also planned, but not yet implemented yet as of 1.10-beta.

Disk chunk full-text index data can not be actually modified, so the
full-text field changes (ie. row deletions and updates) suppress a previous
row version from a disk chunk using a kill-list, but do not actually
physically purge the data. Therefore, on workloads with high full-text
updates ratio index might eventually get polluted by these previous row
versions, and searching performance would degrade. Physical index purging
that would improve the performance is planned, but not yet implemented as
of 1.10-beta.

Data in RAM chunk gets saved to disk on clean daemon shutdown, and then
loaded back on startup. However, on daemon or server crash, updates from
RAM chunk might be lost. To prevent that, binary logging of transactions
can be used; see Section 4.4, <<Binary logging>> for details.

Full-text changes in RT index are transactional. They are stored in
a per-thread accumulator until COMMIT, then applied at once. Bigger batches
per single COMMIT should result in faster indexing.

4.4. Binary logging
===================

Binary logs are essentially a recovery mechanism. With binary logs enabled,
searchd writes every given transaction to the binlog file, and uses that
for recovery after an unclean shutdown. On clean shutdown, RAM chunks are
saved to disk, and then all the binlog files are unlinked.

During normal operation, a new binlog file will be opened every time when
binlog_max_log_size limit is reached. Older, already closed binlog files
are kept until all of the transactions stored in them (from all indexes)
are flushed as a disk chunk. Setting the limit to 0 pretty much prevents
binlog from being unlinked at all while searchd is running; however, it
will still be unlinked on clean shutdown. (This is the default case as of
2.0.3-release, binlog_max_log_size defaults to 0.)

There are 3 different binlog flushing strategies, controlled by
binlog_flush directive which takes the values of 0, 1, or 2. 0 means to
flush the log to OS and sync it to disk every second; 1 means flush and
sync every transaction; and 2 (the default mode) means flush every
transaction but sync every second. Sync is relatively slow because it has
to perform physical disk writes, so mode 1 is the safest (every committed
transaction is guaranteed to be written on disk) but the slowest. Flushing
log to OS prevents from data loss on searchd crashes but not system
crashes. Mode 2 is the default.

On recovery after an unclean shutdown, binlogs are replayed and all logged
transactions since the last good on-disk state are restored. Transactions
are checksummed so in case of binlog file corruption garbage data will not
be replayed; such a broken transaction will be detected and, currently,
will stop replay. Transactions also start with a magic marker and
timestamped, so in case of binlog damage in the middle of the file, it's
technically possible to skip broken transactions and keep replaying from
the next good one, and/or it's possible to replay transactions until
a given timestamp (point-in-time recovery), but none of that is implemented
yet as of 1.10-beta.

One unwanted side effect of binlogs is that actively updating a small RT
index that fully fits into a RAM chunk part will lead to an ever-growing
binlog that can never be unlinked until clean shutdown. Binlogs are
essentially append-only deltas against the last known good saved state on
disk, and unless RAM chunk gets saved, they can not be unlinked. An
ever-growing binlog is not very good for disk use and crash recovery time.
Starting with 2.0.1-beta you can configure searchd to perform a periodic
RAM chunk flush to fix that problem using a rt_flush_period directive. With
periodic flushes enabled, searchd will keep a separate thread, checking
whether RT indexes RAM chunks need to be written back to disk. Once that
happens, the respective binlogs can be (and are) safely unlinked.

Note that rt_flush_period only controls the frequency at which the checks
happen. There are no guarantees that the particular RAM chunk will get
saved. For instance, it does not make sense to regularly re-save a huge RAM
chunk that only gets a few rows worh of updates. The search daemon
determine whether to actually perform the flush with a few heuristics.

Chapter 5. Searching
====================

Table of Contents

5.1. Matching modes
5.2. Boolean query syntax
5.3. Extended query syntax
5.4. Search results ranking
5.5. Expressions, functions, and operators
   5.5.1. Operators
   5.5.2. Numeric functions
   5.5.3. Date and time functions
   5.5.4. Type conversion functions
   5.5.5. Comparison functions
   5.5.6. Miscellaneous functions

5.6. Sorting modes
5.7. Grouping (clustering) search results
5.8. Distributed searching
5.9. searchd query log formats
   5.9.1. Plain log format
   5.9.2. SphinxQL log format

5.10. MySQL protocol support and SphinxQL
5.11. Multi-queries
5.12. Collations
5.13. User-defined functions (UDF)

5.1. Matching modes
===================

So-called matching modes are a legacy feature that used to provide (very)
limited query syntax and ranking support. Currently, they are deprecated in
favor of full-text query language and so-called rankers. Starting with
version 0.9.9-release, it is thus strongly recommended to use
SPH_MATCH_EXTENDED and proper query syntax rather than any other legacy
mode. All those other modes are actually internally converted to extended
syntax anyway. SphinxAPI still defaults to SPH_MATCH_ALL but that is for
compatibility reasons only.

There are the following matching modes available:

   * SPH_MATCH_ALL, matches all query words (default mode);
   * SPH_MATCH_ANY, matches any of the query words;
   * SPH_MATCH_PHRASE, matches query as a phrase, requiring perfect match;
   * SPH_MATCH_BOOLEAN, matches query as a boolean expression (see
     Section 5.2, <<Boolean query syntax>>);
   * SPH_MATCH_EXTENDED, matches query as an expression in Sphinx internal
     query language (see Section 5.3, <<Extended query syntax>>);
   * SPH_MATCH_EXTENDED2, an alias for SPH_MATCH_EXTENDED;
   * SPH_MATCH_FULLSCAN, matches query, forcibly using the "full scan" mode
     as below. NB, any query terms will be ignored, such that filters,
     filter-ranges and grouping will still be applied, but no
     text-matching.

SPH_MATCH_EXTENDED2 was used during 0.9.8 and 0.9.9 development cycle, when
the internal matching engine was being rewritten (for the sake of
additional functionality and better performance). By 0.9.9-release, the
older version was removed, and SPH_MATCH_EXTENDED and SPH_MATCH_EXTENDED2
are now just aliases.

The SPH_MATCH_FULLSCAN mode will be automatically activated in place of the
specified matching mode when the following conditions are met:

   1. The query string is empty (ie. its length is zero).
   2. docinfo storage is set to extern.

In full scan mode, all the indexed documents will be considered as
matching. Such queries will still apply filters, sorting, and group by, but
will not perform any full-text searching. This can be useful to unify
full-text and non-full-text searching code, or to offload SQL server (there
are cases when Sphinx scans will perform better than analogous MySQL
queries). An example of using the full scan mode might be to find posts in
a forum. By selecting the forum's user ID via SetFilter() but not actually
providing any search text, Sphinx will match every document (i.e. every
post) where SetFilter() would match - in this case providing every post
from that user. By default this will be ordered by relevancy, followed by
Sphinx document ID in ascending order (earliest first).

5.2. Boolean query syntax
=========================

Boolean queries allow the following special operators to be used:

   * explicit operator AND:

      | hello & world

   * operator OR:

      | hello | world

   * operator NOT:

      | hello -world
      | hello !world

   * grouping:

      | ( hello world )

Here's an example query which uses all these operators:

Example 5.1. Boolean query example

   | ( cat -dog ) | ( cat -mouse)

There always is implicit AND operator, so "hello world" query actually
means "hello & world".

OR operator precedence is higher than AND, so "looking for cat | dog |
mouse" means "looking for ( cat | dog | mouse )" and not "(looking for cat)
| dog | mouse".

Queries like "-dog", which implicitly include all documents from the
collection, can not be evaluated. This is both for technical and
performance reasons. Technically, Sphinx does not always keep a list of all
IDs. Performance-wise, when the collection is huge (ie. 10-100M documents),
evaluating such queries could take very long.

5.3. Extended query syntax
==========================

The following special operators and modifiers can be used when using the
extended matching mode:

   * operator OR:

      | hello | world

   * operator NOT:

      | hello -world
      | hello !world

   * field search operator:

      | @title hello @body world

   * field position limit modifier (introduced in version 0.9.9-rc1):

      | @body[50] hello

   * multiple-field search operator:

      | @(title,body) hello world

   * ignore field search operator (will ignore any matches of 'hello world'
     from field 'title'):

      | @!title hello world

   * ignore multiple-field search operator (if we have fields title,
     subject and body then @!(title) is equivalent to @(subject,body)):

      | @!(title,body) hello world

   * all-field search operator:

      | @* hello

   * phrase search operator:

      | "hello world"

   * proximity search operator:

      | "hello world"~10

   * quorum matching operator:

      | "the world is a wonderful place"/3

   * strict order operator (aka operator "before"):

      | aaa << bbb << ccc

   * exact form modifier (introduced in version 0.9.9-rc1):

      | raining =cats and =dogs

   * field-start and field-end modifier (introduced in version 0.9.9-rc2):

      | ^hello world$

   * NEAR, generalized proximity operator (introduced in version
     2.0.1-beta):

      | hello NEAR/3 world NEAR/4 "my test"

   * SENTENCE operator (introduced in version 2.0.1-beta):

      | all SENTENCE words SENTENCE "in one sentence"

   * PARAGRAPH operator (introduced in version 2.0.1-beta):

      | "Bill Gates" PARAGRAPH "Steve Jobs"

   * zone limit operator:

      | ZONE:(h3,h4) only in these titles

Here's an example query that uses some of these operators:

Example 5.2. Extended matching mode: query example

   | "hello world" @title "example program"~5 @body python -(php|perl) @* code

The full meaning of this search is:

   * Find the words 'hello' and 'world' adjacently in any field in
     a document;
   * Additionally, the same document must also contain the words 'example'
     and 'program' in the title field, with up to, but not including,
     5 words between the words in question; (E.g. "example PHP program"
     would be matched however "example script to introduce outside data
     into the correct context for your program" would not because two terms
     have 5 or more words between them)
   * Additionally, the same document must contain the word 'python' in the
     body field, but not contain either 'php' or 'perl';
   * Additionally, the same document must contain the word 'code' in any
     field.

There always is implicit AND operator, so "hello world" means that both
"hello" and "world" must be present in matching document.

OR operator precedence is higher than AND, so "looking for cat | dog |
mouse" means "looking for ( cat | dog | mouse )" and not "(looking for cat)
| dog | mouse".

Field limit operator limits subsequent searching to a given field.
Normally, query will fail with an error message if given field name does
not exist in the searched index. However, that can be suppressed by
specifying "@@relaxed" option at the very beginning of the query:

   | @@relaxed @nosuchfield my query

This can be helpful when searching through heterogeneous indexes with
different schemas.

Field position limit, introduced in version 0.9.9-rc1, additionaly
restricts the searching to first N position within given field (or fields).
For example, "@body[50] hello" will not match the documents where the
keyword 'hello' occurs at position 51 and below in the body.

Proximity distance is specified in words, adjusted for word count, and
applies to all words within quotes. For instance, "cat dog mouse"~5 query
means that there must be less than 8-word span which contains all 3 words,
ie. "CAT aaa bbb ccc DOG eee fff MOUSE" document will not match this query,
because this span is exactly 8 words long.

Quorum matching operator introduces a kind of fuzzy matching. It will only
match those documents that pass a given threshold of given words. The
example above ("the world is a wonderful place"/3) will match all documents
that have at least 3 of the 6 specified words.

Strict order operator (aka operator "before"), introduced in version
0.9.9-rc2, will match the document only if its argument keywords occur in
the document exactly in the query order. For instance, "black << cat" query
(without quotes) will match the document "black and white cat" but not the
"that cat was black" document. Order operator has the lowest priority. It
can be applied both to just keywords and more complex expressions, ie. this
is a valid query:

   | (bag of words) << "exact phrase" << red|green|blue

Exact form keyword modifier, introduced in version 0.9.9-rc1, will match
the document only if the keyword occurred in exactly the specified form.
The default behaviour is to match the document if the stemmed keyword
matches. For instance, "runs" query will match both the document that
contains "runs" and the document that contains "running", because both
forms stem to just "run" - while "=runs" query will only match the first
document. Exact form operator requires index_exact_words option to be
enabled. This is a modifier that affects the keyword and thus can be used
within operators such as phrase, proximity, and quorum operators.

Field-start and field-end keyword modifiers, introduced in version
0.9.9-rc2, will make the keyword match only if it occurred at the very
start or the very end of a fulltext field, respectively. For instance, the
query "^hello world$" (with quotes and thus combining phrase operator and
start/end modifiers) will only match documents that contain at least one
field that has exactly these two keywords.

Starting with 0.9.9-rc1, arbitrarily nested brackets and negations are
allowed. However, the query must be possible to compute without involving
an implicit list of all documents:

   | // correct query
   | aaa -(bbb -(ccc ddd))
   | 
   | // queries that are non-computable
   | -aaa
   | aaa | -bbb

NEAR operator, added in 2.0.1-beta, is a generalized version of a proximity
operator. The syntax is NEAR/N, it is case-sensitive, and no spaces are
allowed beetwen the NEAR keyword, the slash sign, and the distance value.

The original proximity operator only worked on sets of keywords. NEAR is
more generic and can accept arbitrary subexpressions as its two arguments,
matching the document when both subexpressions are found within N words of
each other, no matter in which order. NEAR is left associative and has the
same (lowest) precedence as BEFORE.

You should also note how a (one NEAR/7 two NEAR/7 three) query using NEAR
is not really equivalent to a ("one two three"~7) one using keyword
proximity operator. The difference here is that the proximity operator
allows for up to 6 non-matching words between all the 3 matching words, but
the version with NEAR is less restrictive: it would allow for up to 6 words
between 'one' and 'two' and then for up to 6 more between that two-word
matching and a 'three' keyword.

SENTENCE and PARAGRAPH operators, added in 2.0.1-beta, matches the document
when both its arguments are within the same sentence or the same paragraph
of text, respectively. The arguments can be either keywords, or phrases, or
the instances of the same operator. Here are a few examples:

   | one SENTENCE two
   | one SENTENCE "two three"
   | one SENTENCE "two three" SENTENCE four

The order of the arguments within the sentence or paragraph does not
matter. These operators only work on indexes built with index_sp (sentence
and paragraph indexing feature) enabled, and revert to a mere AND
otherwise. Refer to the index_sp directive documentation for the notes on
what's considered a sentence and a paragraph.

ZONE limit operator, added in 2.0.1-beta, is quite similar to field limit
operator, but restricts matching to a given in-field zone or a list of
zones. Note that the subsequent subexpressions are not required to match in
a single contiguous span of a given zone, and may match in multiple spans.
For instance, (ZONE:th hello world) query will match this example document:

   | <th>Table 1. Local awareness of Hello Kitty brand.</th>
   | .. some table data goes here ..
   | <th>Table 2. World-wide brand awareness.</th>

ZONE operator affects the query until the next field or ZONE limit
operator, or the closing parenthesis. It only works on the indexes built
with zones support (see Section 11.2.9, <<index_zones>>) and will be
ignored otherwise.

5.4. Search results ranking
===========================

Ranking overview
----------------

Ranking (aka weighting) of the search results can be defined as a process
of computing a so-called relevance (aka weight) for every given matched
document with regards to a given query that matched it. So relevance is in
the end just a number attached to every document that estimates how
relevant the document is to the query. Search results can then be sorted
based on this number and/or some additional parameters, so that the most
sought after results would come up higher on the results page.

There is no single standard one-size-fits-all way to rank any document in
any scenario. Moreover, there can not ever be such a way, because relevance
is subjective. As in, what seems relevant to you might not seem relevant to
me. Hence, in general case it's not just hard to compute, it's
theoretically impossible.

So ranking in Sphinx is configurable. It has a notion of a so-called
ranker. A ranker can formally be defined as a function that takes document
and query as its input and produces a relevance value as output. In
layman's terms, a ranker controls exactly how (using which specific
algorithm) will Sphinx assign weights to the document.

Previously, this ranking function was rigidly bound to the matching mode.
So in the legacy matching modes (that is, SPH_MATCH_ALL, SPH_MATCH_ANY,
SPH_MATCH_PHRASE, and SPH_MATCH_BOOLEAN) you can not choose the ranker. You
can only do that in the SPH_MATCH_EXTENDED mode. (Which is the only mode in
SphinxQL and the suggested mode in SphinxAPI anyway.) To choose
a non-default ranker you can either use SetRankingMode() with SphinxAPI, or
OPTION ranker clause in SELECT statement when using SphinxQL.

As a sidenote, legacy matching modes are internally implemented via the
unified syntax anyway. When you use one of those modes, Sphinx just
internally adjusts the query and sets the associated ranker, then executes
the query using the very same unified code path.

Available rankers
-----------------

Sphinx ships with a number of built-in rankers suited for different
purposes. A number of them uses two factors, phrase proximity (aka LCS) and
BM25. Phrase proximity works on the keyword positions, while BM25 works on
the keyword frequencies. Basically, the better the degree of the phrase
match between the document body and the query, the higher is the phrase
proximity (it maxes out when the document contains the entire query as
a verbatim quote). And BM25 is higher when the document contains more rare
words. We'll save the detailed discussion for later.

Currently implemented rankers are:

   * SPH_RANK_PROXIMITY_BM25, the default ranking mode that uses and
     combines both phrase proximity and BM25 ranking.
   * SPH_RANK_BM25, statistical ranking mode which uses BM25 ranking only
     (similar to most other full-text engines). This mode is faster but may
     result in worse quality on queries which contain more than 1 keyword.
   * SPH_RANK_NONE, no ranking mode. This mode is obviously the fastest.
     A weight of 1 is assigned to all matches. This is sometimes called
     boolean searching that just matches the documents but does not rank
     them.
   * SPH_RANK_WORDCOUNT, ranking by the keyword occurrences count. This
     ranker computes the per-field keyword occurrence counts, then
     multiplies them by field weights, and sums the resulting values.
   * SPH_RANK_PROXIMITY, added in version 0.9.9-rc1, returns raw phrase
     proximity value as a result. This mode is internally used to emulate
     SPH_MATCH_ALL queries.
   * SPH_RANK_MATCHANY, added in version 0.9.9-rc1, returns rank as it was
     computed in SPH_MATCH_ANY mode ealier, and is internally used to
     emulate SPH_MATCH_ANY queries.
   * SPH_RANK_FIELDMASK, added in version 0.9.9-rc2, returns a 32-bit mask
     with N-th bit corresponding to N-th fulltext field, numbering from 0.
     The bit will only be set when the respective field has any keyword
     occurences satisfiying the query.
   * SPH_RANK_SPH04, added in version 1.10-beta, is generally based on the
     default SPH_RANK_PROXIMITY_BM25 ranker, but additionally boosts the
     matches when they occur in the very beginning or the very end of
     a text field. Thus, if a field equals the exact query, SPH04 should
     rank it higher than a field that contains the exact query but is not
     equal to it. (For instance, when the query is "Hyde Park", a document
     entitled "Hyde Park" should be ranked higher than a one entitled "Hyde
     Park, London" or "The Hyde Park Cafe".)
   * SPH_RANK_EXPR, added in version 2.0.2-beta, lets you specify the
     ranking formula in run time. It exposes a number of internal text
     factors and lets you define how the final weight should be computed
     from those factors. You can find more details about its syntax and
     a reference available factors in a subsection below.

You should specify the SPH_RANK_ prefix and use capital letters only when
using the SetRankingMode() call from the SphinxAPI. The API ports expose
these as global constants. Using SphinxQL syntax, the prefix should be
omitted and the ranker name is case insensitive. Example:

   | // SphinxAPI
   | $client->SetRankingMode ( SPH_RANK_SPH04 );
   | 
   | // SphinxQL
   | mysql_query ( "SELECT ... OPTION ranker=sph04" );

Legacy matching modes rankers
-----------------------------

Legacy matching modes automatically select a ranker as follows:

   * SPH_MATCH_ALL uses SPH_RANK_PROXIMITY ranker;
   * SPH_MATCH_ANY uses SPH_RANK_MATCHANY ranker;
   * SPH_MATCH_PHRASE uses SPH_RANK_PROXIMITY ranker;
   * SPH_MATCH_BOOLEAN uses SPH_RANK_NONE ranker.

Expression based ranker (SPH_RANK_EXPR)
---------------------------------------

Expression ranker, added in version 2.0.2-beta, lets you change the ranking
formula on the fly, on a per-query basis. For a quick kickoff, this is how
you emulate PROXIMITY_BM25 ranker using the expression based one:

   | SELECT *, WEIGHT() FROM myindex WHERE MATCH('hello world')
   | OPTION ranker=expr('sum(lcs*user_weight)*1000+bm25')

The output of this query must not change if you omit the OPTION clause,
because the default ranker (PROXIMITY_BM25) behaves exactly like specified
in the ranker formula above. But the expression ranker is somewhat more
flexible than just that and provides access to many more factors.

The ranking formula is an arbitrary arithmetic expression that can use
constants, document attributes, built-in functions and operators (described
in Section 5.5, <<Expressions, functions, and operators>>), and also a few
ranking-specific things that are only accessible in a ranking formula.
Namely, those are field aggregation functions, field-level, and
document-level ranking factors.

A document-level factor is a numeric value computed by the ranking engine
for every matched document with regards to the current query. (So it
differs from a plain document attribute in that the attribute do not depend
on the full text query, while factors might.) Those factors can be used
anywhere in the ranking expression. Currently implemented document-level
factors are:

   * bm25 (integer), a document-level BM25 estimate (computed without
     keyword occurrence filtering).
   * max_lcs (integer), a query-level maximum possible value that the
     sum(lcs*user_weight) expression can ever take. This can be useful for
     weight boost scaling. For instance, MATCHANY ranker formula uses this
     to guarantee that a full phrase match in any field rankes higher than
     any combination of partial matches in all fields.
   * field_mask (integer), a document-level 32-bit mask of matched fields.
   * query_word_count (integer), the number of unique keywords in a query,
     adjusted for a number of excluded keywords. For instance, both (one
     one one one) and (one !two) queries should assign a value of 1 to this
     factor, because there is just one unique non-excluded keyword.
   * doc_word_count (integer), the number of unique keywords matched in the
     entire document.

A field-level factor is a numeric value computed by the ranking engine for
every matched in-document text field with regards to the current query. As
more than one field can be matched by a query, but the final weight needs
to be a single integer value, these values need to be folded into a single
one. To achieve that, field-level factors can only be used within a field
aggregation function, they can not be used anywhere in the expression. For
example, you can not use (lcs+bm25) as your ranking expression, as lcs
takes multiple values (one in every matched field). You should use
(sum(lcs)+bm25) instead, that expression sums lcs over all matching fields,
and then adds bm25 to that per-field sum. Currently implemented field-level
factors are:

   * lcs (integer), the length of a maximum verbatim match between the
     document and the query, counted in words. LCS stands for Longest
     Common Subsequence (or Subset). Takes a minimum value of 1 when only
     stray keywords were matched in a field, and a maximum value of query
     keywords count when the entire query was matched in a field verbatim
     (in the exact query keywords order). For example, if the query is
     'hello world' and the field contains these two words quoted from the
     query (that is, adjacent to each other, and exactly in the query
     order), lcs will be 2. For example, if the query is 'hello world
     program' and the field contains 'hello world', lcs will be 2. Note
     that any subset of the query keyword works, not just a subset of
     adjacent keywords. For example, if the query is 'hello world program'
     and the field contains 'hello (test program)', lcs will be 2 just as
     well, because both 'hello' and 'program' matched in the same
     respective positions as they were in the query. Finally, if the query
     is 'hello world program' and the field contains 'hello world program',
     lcs will be 3. (Hopefully that is unsurprising at this point.)
   * user_weight (integer), the user specified per-field weight (refer to
     SetFieldWeights() in SphinxAPI and OPTION field_weights in SphinxQL
     respectively). The weights default to 1 if not specified explicitly.
   * hit_count (integer), the number of keyword occurrences that matched in
     the field. Note that a single keyword may occur multiple times. For
     example, if 'hello' occurs 3 times in a field and 'world' occurs
     5 times, hit_count will be 8.
   * word_count (integer), the number of unique keywords matched in the
     field. For example, if 'hello' and 'world' occur anywhere in a field,
     word_count will be 2, irregardless of how many times do both keywords
     occur.
   * tf_idf (float), the sum of TF*IDF over all the keywords matched in the
     field. IDF is the Inverse Document Frequency, a floating point value
     between 0 and 1 that describes how frequent is the keywords
     (basically, 0 for a keyword that occurs in every document indexed, and
     1 for a unique keyword that occurs in just a single document). TF is
     the Term Frequency, the number of matched keyword occurrences in the
     field. As a side note, tf_idf is actually computed by summing IDF over
     all matched occurences. That's by construction equivalent to summing
     TF*IDF over all matched keywords.
   * min_hit_pos (integer), the position of the first matched keyword
     occurrence, counted in words. Indexing begins from position 1.
   * min_best_span_pos (integer), the position of the first maximum LCS
     occurrences span. For example, assume that our query was 'hello world
     program' and 'hello world' subphrase was matched twice in the field,
     in positions 13 and 21. Assume that 'hello' and 'world' additionally
     occurred elsewhere in the field, but never next to each other and thus
     never as a subphrase match. In that case, min_best_span_pos will be
     13. Note how for the single keyword queries min_best_span_pos will
     always equal min_hit_pos.
   * exact_hit (boolean), whether a query was an exact match of the entire
     current field. Used in the SPH04 ranker.

A field aggregation function is a single argument function that takes an
expression with field-level factors, iterates it over all the matched
fields, and computes the final results. Currently implemented field
aggregation functions are:

   * sum, sums the argument expression over all matched fields. For
     instance, sum(1) should return a number of matched fields.

Expressions for the built-in rankers
------------------------------------

Most of the other rankers can actually be emulated with the expression
based ranker. You just need to pass a proper expression. Such emulation is,
of course, going to be slower than using the built-in, compiled ranker but
still might be of interest if you want to fine-tune your ranking formula
starting with one of the existing ones. Also, the formulas define the nitty
gritty ranker details in a nicely readable fashion.

   * SPH_RANK_PROXIMITY_BM25 = sum(lcs*user_weight)*1000+bm25
   * SPH_RANK_BM25 = bm25
   * SPH_RANK_NONE = 1
   * SPH_RANK_WORDCOUNT = sum(hit_count*user_weight)
   * SPH_RANK_PROXIMITY = sum(lcs*user_weight)
   * SPH_RANK_MATCHANY = sum((word_count+(lcs-1)*max_lcs)*user_weight)
   * SPH_RANK_FIELDMASK = field_mask
   * SPH_RANK_SPH04 =
     sum((4*lcs+2*(min_hit_pos==1)+exact_hit)*user_weight)*1000+bm25

5.5. Expressions, functions, and operators
==========================================

Sphinx lets you use arbitrary arithmetic expressions both via SphinxQL and
SphinxAPI, involving attribute values, internal attributes (document ID and
relevance weight), arithmetic operations, a number of built-in functions,
and user-defined functions. This section documents the supported operators
and functions. Here's the complete reference list for quick access.

   * Arithmetic operators: +, -, *, /, %, DIV, MOD
   * Comparison operators: <, > <=, >=, =, <>
   * Boolean operators: AND, OR, NOT
   * Bitwise operators: &, |
   * ABS()
   * BIGINT()
   * CEIL()
   * COS()
   * CRC32()
   * DAY()
   * EXP()
   * FIBONACCI()
   * FLOOR()
   * GEODIST()
   * IDIV()
   * IF()
   * IN()
   * INTERVAL()
   * LN()
   * LOG10()
   * LOG2()
   * MAX()
   * MIN()
   * MONTH()
   * NOW()
   * POW()
   * SIN()
   * SINT()
   * SQRT()
   * YEAR()
   * YEARMONTH()
   * YEARMONTHDAY()

5.5.1. Operators
----------------

Arithmetic operators: +, -, *, /, %, DIV, MOD
   The standard arithmetic operators. Arithmetic calculations involving
   those can be performed in three different modes: (a) using
   single-precision, 32-bit IEEE 754 floating point values (the default),
   (b) using signed 32-bit integers, (c) using 64-bit signed integers. The
   expression parser will automatically switch to integer mode if there are
   no operations the result in a floating point value. Otherwise, it will
   use the default floating point mode. For instance, a+b will be computed
   using 32-bit integers if both arguments are 32-bit integers; or using
   64-bit integers if both arguments are integers but one of them is
   64-bit; or in floats otherwise. However, a/b or sqrt(a) will always be
   computed in floats, because these operations return a result of
   non-integer type. To avoid the first, you can either use IDIV(a,b) or
   a DIV b form. Also, a*b will not be automatically promoted to 64-bit
   when the arguments are 32-bit. To enforce 64-bit results, you can use
   BIGINT(). (But note that if there are non-integer operations, BIGINT()
   will simply be ignored.)

Comparison operators: <, > <=, >=, =, <>
   Comparison operators (eg. = or <=) return 1.0 when the condition is true
   and 0.0 otherwise. For instance, (a=b)+3 will evaluate to 4 when
   attribute 'a' is equal to attribute 'b', and to 3 when 'a' is not.
   Unlike MySQL, the equality comparisons (ie. = and <> operators)
   introduce a small equality threshold (1e-6 by default). If the
   difference between compared values is within the threshold, they will be
   considered equal.

Boolean operators: AND, OR, NOT
   Boolean operators (AND, OR, NOT) were introduced in 0.9.9-rc2 and behave
   as usual. They are left-associative and have the least priority compared
   to other operators. NOT has more priority than AND and OR but
   nevertheless less than any other operator. AND and OR have the same
   priority so brackets use is recommended to avoid confusion in complex
   expressions.

Bitwise operators: &, |
   These operators perform bitwise AND and OR respectively. The operands
   must be of an integer types. Introduced in version 1.10-beta.

5.5.2. Numeric functions
------------------------

ABS()
   Returns the absolute value of the argument.

CEIL()
   Returns the smallest integer value greater or equal to the argument.

COS()
   Returns the cosine of the argument.

EXP()
   Returns the exponent of the argument (e=2.718... to the power of the
   argument).

FIBONACCI()
   Returns the N-th Fibonacci number, where N is the integer argument. That
   is, arguments of 0 and up will generate the values 0, 1, 1, 2, 3, 5, 8,
   13 and so on. Note that the computations are done using 32-bit integer
   math and thus numbers 48th and up will be returned modulo 2^32.

FLOOR()
   Returns the largest integer value lesser or equal to the argument.

IDIV()
   Returns the result of an integer division of the first argument by the
   second argument. Both arguments must be of an integer type.

LN()
   Returns the natural logarithm of the argument (with the base of
   e=2.718...).

LOG10()
   Returns the common logarithm of the argument (with the base of 10).

LOG2()
   Returns the binary logarithm of the argument (with the base of 2).

MAX()
   Returns the bigger of two arguments.

MIN()
   Returns the smaller of two arguments.

POW()
   Returns the first argument raised to the power of the second argument.

SIN()
   Returns the sine of the argument.

SQRT()
   Returns the square root of the argument.

5.5.3. Date and time functions
------------------------------

DAY()
   Returns the integer day of month (in 1..31 range) from a timestamp
   argument, according to the current timezone. Introduced in version
   2.0.1-beta.

MONTH()
   Returns the integer month (in 1..12 range) from a timestamp argument,
   according to the current timezone. Introduced in version 2.0.1-beta.

NOW()
   Returns the current timestamp as an INTEGER. Introduced in version
   0.9.9-rc1.

YEAR()
   Returns the integer year (in 1969..2038 range) from a timestamp
   argument, according to the current timezone. Introduced in version
   2.0.1-beta.

YEARMONTH()
   Returns the integer year and month code (in 196912..203801 range) from
   a timestamp argument, according to the current timezone. Introduced in
   version 2.0.1-beta.

YEARMONTHDAY()
   Returns the integer year, month, and date code (in 19691231..20380119
   range) from a timestamp argument, according to the current timezone.
   Introduced in version 2.0.1-beta.

5.5.4. Type conversion functions
--------------------------------

BIGINT()
   Forcibly promotes the integer argument to 64-bit type, and does nothing
   on floating point argument. It's intended to help enforce evaluation of
   certain expressions (such as a*b) in 64-bit mode even though all the
   arguments are 32-bit. Introduced in version 0.9.9-rc1.

SINT()
   Forcibly reinterprets its 32-bit unsigned integer argument as signed,
   and also expands it to 64-bit type (because 32-bit type is unsigned).
   It's easily illustrated by the following example: 1-2 normally evaluates
   to 4294967295, but SINT(1-2) evaluates to -1. Introduced in version
   1.10-beta.

5.5.5. Comparison functions
---------------------------

IF()
   IF() behavior is slightly different that that of its MySQL counterpart.
   It takes 3 arguments, check whether the 1st argument is equal to 0.0,
   returns the 2nd argument if it is not zero, or the 3rd one when it is.
   Note that unlike comparison operators, IF() does not use a threshold!
   Therefore, it's safe to use comparison results as its 1st argument, but
   arithmetic operators might produce unexpected results. For instance, the
   following two calls will produce different results even though they are
   logically equivalent:

      | IF ( sqrt(3)*sqrt(3)-3<>0, a, b )
      | IF ( sqrt(3)*sqrt(3)-3, a, b )

   In the first case, the comparison operator <> will return 0.0 (false)
   because of a threshold, and IF() will always return 'b' as a result. In
   the second one, the same sqrt(3)*sqrt(3)-3 expression will be compared
   with zero without threshold by the IF() function itself. But its value
   will be slightly different from zero because of limited floating point
   calculations precision. Because of that, the comparison with 0.0 done by
   IF() will not pass, and the second variant will return 'a' as a result.

IN()
   IN(expr,val1,val2,...), introduced in version 0.9.9-rc1, takes 2 or more
   arguments, and returns 1 if 1st argument (expr) is equal to any of the
   other arguments (val1..valN), or 0 otherwise. Currently, all the checked
   values (but not the expression itself!) are required to be constant.
   (Its technically possible to implement arbitrary expressions too, and
   that might be implemented in the future.) Constants are pre-sorted and
   then binary search is used, so IN() even against a big arbitrary list of
   constants will be very quick. Starting with 0.9.9-rc2, first argument
   can also be a MVA attribute. In that case, IN() will return 1 if any of
   the MVA values is equal to any of the other arguments. Starting with
   2.0.1-beta, IN() also supports IN(expr,@uservar) syntax to check whether
   the value belongs to the list in the given global user variable.

INTERVAL()
   INTERVAL(expr,point1,point2,point3,...), introduced in version
   0.9.9-rc1, takes 2 or more arguments, and returns the index of the
   argument that is less than the first argument: it returns 0 if
   expr<point1, 1 if point1<=expr<point2, and so on. It is required that
   point1<point2<...<pointN for this function to work correctly.

5.5.6. Miscellaneous functions
------------------------------

CRC32()
   Returns the CRC32 value of a string argument. Introduced in version
   2.0.1-beta.

GEODIST()
   GEODIST(lat1,long1,lat2,long2) function, introduced in version
   0.9.9-rc2, computes geosphere distance between two given points
   specified by their coordinates. Note that both latitudes and longitudes
   must be in radians and the result will be in meters. You can use
   arbitrary expression as any of the four coordinates. An optimized path
   will be selected when one pair of the arguments refers directly to
   a pair attributes and the other one is constant.

5.6. Sorting modes
==================

There are the following result sorting modes available:

   * SPH_SORT_RELEVANCE mode, that sorts by relevance in descending order
     (best matches first);
   * SPH_SORT_ATTR_DESC mode, that sorts by an attribute in descending
     order (bigger attribute values first);
   * SPH_SORT_ATTR_ASC mode, that sorts by an attribute in ascending order
     (smaller attribute values first);
   * SPH_SORT_TIME_SEGMENTS mode, that sorts by time segments (last
     hour/day/week/month) in descending order, and then by relevance in
     descending order;
   * SPH_SORT_EXTENDED mode, that sorts by SQL-like combination of columns
     in ASC/DESC order;
   * SPH_SORT_EXPR mode, that sorts by an arithmetic expression.

SPH_SORT_RELEVANCE ignores any additional parameters and always sorts
matches by relevance rank. All other modes require an additional sorting
clause, with the syntax depending on specific mode. SPH_SORT_ATTR_ASC,
SPH_SORT_ATTR_DESC and SPH_SORT_TIME_SEGMENTS modes require simply an
attribute name. SPH_SORT_RELEVANCE is equivalent to sorting by "@weight
DESC, @id ASC" in extended sorting mode, SPH_SORT_ATTR_ASC is equivalent to
"attribute ASC, @weight DESC, @id ASC", and SPH_SORT_ATTR_DESC to
"attribute DESC, @weight DESC, @id ASC" respectively.

SPH_SORT_TIME_SEGMENTS mode
---------------------------

In SPH_SORT_TIME_SEGMENTS mode, attribute values are split into so-called
time segments, and then sorted by time segment first, and by relevance
second.

The segments are calculated according to the current timestamp at the time
when the search is performed, so the results would change over time. The
segments are as follows:

   * last hour,
   * last day,
   * last week,
   * last month,
   * last 3 months,
   * everything else.

These segments are hardcoded, but it is trivial to change them if
necessary.

This mode was added to support searching through blogs, news headlines,
etc. When using time segments, recent records would be ranked higher
because of segment, but withing the same segment, more relevant records
would be ranked higher - unlike sorting by just the timestamp attribute,
which would not take relevance into account at all.

SPH_SORT_EXTENDED mode
----------------------

In SPH_SORT_EXTENDED mode, you can specify an SQL-like sort expression with
up to 5 attributes (including internal attributes), eg:

   | @relevance DESC, price ASC, @id DESC

Both internal attributes (that are computed by the engine on the fly) and
user attributes that were configured for this index are allowed. Internal
attribute names must start with magic @-symbol; user attribute names can be
used as is. In the example above, @relevance and @id are internal
attributes and price is user-specified.

Known internal attributes are:

   * @id (match ID)
   * @weight (match weight)
   * @rank (match weight)
   * @relevance (match weight)
   * @random (return results in random order)

@rank and @relevance are just additional aliases to @weight.

SPH_SORT_EXPR mode
------------------

Expression sorting mode lets you sort the matches by an arbitrary
arithmetic expression, involving attribute values, internal attributes (@id
and @weight), arithmetic operations, and a number of built-in functions.
Here's an example:

   | $cl->SetSortMode ( SPH_SORT_EXPR,
   | 	"@weight + ( user_karma + ln(pageviews) )*0.1" );

The operators and functions supported in the expressions are discussed in
a separate section, Section 5.5, <<Expressions, functions, and operators>>.

5.7. Grouping (clustering) search results
=========================================

Sometimes it could be useful to group (or in other terms, cluster) search
results and/or count per-group match counts - for instance, to draw a nice
graph of how much maching blog posts were there per each month; or to group
Web search results by site; or to group matching forum posts by author;
etc.

In theory, this could be performed by doing only the full-text search in
Sphinx and then using found IDs to group on SQL server side. However, in
practice doing this with a big result set (10K-10M matches) would typically
kill performance.

To avoid that, Sphinx offers so-called grouping mode. It is enabled with
SetGroupBy() API call. When grouping, all matches are assigned to different
groups based on group-by value. This value is computed from specified
attribute using one of the following built-in functions:

   * SPH_GROUPBY_DAY, extracts year, month and day in YYYYMMDD format from
     timestamp;
   * SPH_GROUPBY_WEEK, extracts year and first day of the week number
     (counting from year start) in YYYYNNN format from timestamp;
   * SPH_GROUPBY_MONTH, extracts month in YYYYMM format from timestamp;
   * SPH_GROUPBY_YEAR, extracts year in YYYY format from timestamp;
   * SPH_GROUPBY_ATTR, uses attribute value itself for grouping.

The final search result set then contains one best match per group.
Grouping function value and per-group match count are returned along as
"virtual" attributes named @group and @count respectively.

The result set is sorted by group-by sorting clause, with the syntax
similar to SPH_SORT_EXTENDED sorting clause syntax. In addition to @id and
@weight, group-by sorting clause may also include:

   * @group (groupby function value),
   * @count (amount of matches in group).

The default mode is to sort by groupby value in descending order, ie. by
"@group desc".

On completion, total_found result parameter would contain total amount of
matching groups over he whole index.

WARNING: grouping is done in fixed memory and thus its results are only
approximate; so there might be more groups reported in total_found than
actually present. @count might also be underestimated. To reduce
inaccuracy, one should raise max_matches. If max_matches allows to store
all found groups, results will be 100% correct.

For example, if sorting by relevance and grouping by "published" attribute
with SPH_GROUPBY_DAY function, then the result set will contain

   * one most relevant match per each day when there were any matches
     published,
   * with day number and per-day match count attached,
   * sorted by day number in descending order (ie. recent days first).

Starting with version 0.9.9-rc2, aggregate functions (AVG(), MIN(), MAX(),
SUM()) are supported through SetSelect() API call when using GROUP BY.

5.8. Distributed searching
==========================

To scale well, Sphinx has distributed searching capabilities. Distributed
searching is useful to improve query latency (ie. search time) and
throughput (ie. max queries/sec) in multi-server, multi-CPU or multi-core
environments. This is essential for applications which need to search
through huge amounts data (ie. billions of records and terabytes of text).

The key idea is to horizontally partition (HP) searched data accross search
nodes and then process it in parallel.

Partitioning is done manually. You should

   * setup several instances of Sphinx programs (indexer and searchd) on
     different servers;
   * make the instances index (and search) different parts of data;
   * configure a special distributed index on some of the searchd
     instances;
   * and query this index.

This index only contains references to other local and remote indexes - so
it could not be directly reindexed, and you should reindex those indexes
which it references instead.

When searchd receives a query against distributed index, it does the
following:

   1. connects to configured remote agents;
   2. issues the query;
   3. sequentially searches configured local indexes (while the remote
      agents are searching);
   4. retrieves remote agents' search results;
   5. merges all the results together, removing the duplicates;
   6. sends the merged resuls to client.

From the application's point of view, there are no differences between
searching through a regular index, or a distributed index at all. That is,
distributed indexes are fully transparent to the application, and actually
there's no way to tell whether the index you queried was distributed or
local. (Even though as of 0.9.9 Sphinx does not allow to combine searching
through distributed indexes with anything else, this constraint will be
lifted in the future.)

Any searchd instance could serve both as a master (which aggregates the
results) and a slave (which only does local searching) at the same time.
This has a number of uses:

   1. every machine in a cluster could serve as a master which searches the
      whole cluster, and search requests could be balanced between masters
      to achieve a kind of HA (high availability) in case any of the nodes
      fails;
   2. if running within a single multi-CPU or multi-core machine, there
      would be only 1 searchd instance quering itself as an agent and thus
      utilizing all CPUs/core.

It is scheduled to implement better HA support which would allow to specify
which agents mirror each other, do health checks, keep track of alive
agents, load-balance requests, etc.

5.9. searchd query log formats
==============================

In version 2.0.1-beta and above two query log formats are supported.
Previous versions only supported a custom plain text format. That format is
still the default one. However, while it might be more convenient for
manual monitoring and review, but hard to replay for benchmarks, it only
logs search queries but not the other types of requests, does not always
contain the complete search query data, etc. The default text format is
also harder (and sometimes impossible) to replay for benchmarking purposes.
The new sphinxql format alleviates that. It aims to be complete and
automatable, even though at the cost of brevity and readability.

5.9.1. Plain log format
-----------------------

By default, searchd logs all succesfully executed search queries into
a query log file. Here's an example:

   | [Fri Jun 29 21:17:58 2007] 0.004 sec [all/0/rel 35254 (0,20)] [lj] test
   | [Fri Jun 29 21:20:34 2007] 0.024 sec [all/0/rel 19886 (0,20) @channel_id] [lj] test

This log format is as follows:

   | [query-date] query-time [match-mode/filters-count/sort-mode
   |     total-matches (offset,limit) @groupby-attr] [index-name] query

Match mode can take one of the following values:

   * "all" for SPH_MATCH_ALL mode;
   * "any" for SPH_MATCH_ANY mode;
   * "phr" for SPH_MATCH_PHRASE mode;
   * "bool" for SPH_MATCH_BOOLEAN mode;
   * "ext" for SPH_MATCH_EXTENDED mode;
   * "ext2" for SPH_MATCH_EXTENDED2 mode;
   * "scan" if the full scan mode was used, either by being specified with
     SPH_MATCH_FULLSCAN, or if the query was empty (as documented under
     Matching Modes)

Sort mode can take one of the following values:

   * "rel" for SPH_SORT_RELEVANCE mode;
   * "attr-" for SPH_SORT_ATTR_DESC mode;
   * "attr+" for SPH_SORT_ATTR_ASC mode;
   * "tsegs" for SPH_SORT_TIME_SEGMENTS mode;
   * "ext" for SPH_SORT_EXTENDED mode.

Additionally, if searchd was started with --iostats, there will be a block
of data after where the index(es) searched are listed.

A query log entry might take the form of:

   | [Fri Jun 29 21:17:58 2007] 0.004 sec [all/0/rel 35254 (0,20)] [lj]
   |    [ios=6 kb=111.1 ms=0.5] test

This additional block is information regarding I/O operations in performing
the search: the number of file I/O operations carried out, the amount of
data in kilobytes read from the index files and time spent on I/O
operations (although there is a background processing component, the bulk
of this time is the I/O operation time).

5.9.2. SphinxQL log format
--------------------------

This is a new log format introduced in 2.0.1-beta, with the goals begin
logging everything and then some, and in a format easy to automate (for
insance, automatically replay). New format can either be enabled via the
query_log_format directive in the configuration file, or switched back and
forth on the fly with the SET GLOBAL query_log_format=... statement via
SphinxQL. In the new format, the example from the previous section would
look as follows. (Wrapped below for readability, but with just one query
per line in the actual log.)

   | /* Fri Jun 29 21:17:58.609 2007 2011 conn 2 wall 0.004 found 35254 */
   | SELECT * FROM lj WHERE MATCH('test') OPTION ranker=proximity;
   | 
   | /* Fri Jun 29 21:20:34 2007.555 conn 3 wall 0.024 found 19886 */
   | SELECT * FROM lj WHERE MATCH('test') GROUP BY channel_id
   | OPTION ranker=proximity;

Note that all requests would be logged in this format, including those sent
via SphinxAPI and SphinxSE, not just those sent via SphinxQL. Also note,
that this kind of logging works only with plain log files and will not work
if you use 'syslog' for logging.

The features of SphinxQL log format compared to the default text one are as
follows.

   * All request types should be logged. (This is still work in progress.)
   * Full statement data will be logged where possible.
   * Errors and warnings are logged.
   * The log should be automatically replayable via SphinxQL.
   * Additional performance counters (currently, per-agent distributed
     query times) are logged.

Every request (including both SphinxAPI and SphinxQL) request must result
in exactly one log line. All request types, including INSERT, CALL
SNIPPETS, etc will eventually get logged, though as of time of this
writing, that is a work in progress). Every log line must be a valid
SphinxQL statement that reconstructs the full request, except if the logged
request is too big and needs shortening for performance reasons. Additional
messages, counters, etc can be logged in the comments section after the
request.

5.10. MySQL protocol support and SphinxQL
=========================================

Starting with version 0.9.9-rc2, Sphinx searchd daemon supports MySQL
binary network protocol and can be accessed with regular MySQL API. For
instance, 'mysql' CLI client program works well. Here's an example of
querying Sphinx using MySQL client:

   | $ mysql -P 9306
   | Welcome to the MySQL monitor.  Commands end with ; or \g.
   | Your MySQL connection id is 1
   | Server version: 0.9.9-dev (r1734)
   | 
   | Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
   | 
   | mysql> SELECT * FROM test1 WHERE MATCH('test') 
   |     -> ORDER BY group_id ASC OPTION ranker=bm25;
   | +------+--------+----------+------------+
   | | id   | weight | group_id | date_added |
   | +------+--------+----------+------------+
   | |    4 |   1442 |        2 | 1231721236 |
   | |    2 |   2421 |      123 | 1231721236 |
   | |    1 |   2421 |      456 | 1231721236 |
   | +------+--------+----------+------------+
   | 3 rows in set (0.00 sec)

Note that mysqld was not even running on the test machine. Everything was
handled by searchd itself.

The new access method is supported in addition to native APIs which all
still work perfectly well. In fact, both access methods can be used at the
same time. Also, native API is still the default access method. MySQL
protocol support needs to be additionally configured. This is a matter of
1-line config change, adding a new listener with mysql41 specified as
a protocol:

   | listen = localhost:9306:mysql41

Just supporting the protocol and not the SQL syntax would be useless so
Sphinx now also supports a subset of SQL that we dubbed SphinxQL. It
supports the standard querying all the index types with SELECT, modifying
RT indexes with INSERT, REPLACE, and DELETE, and much more. Full SphinxQL
reference is available in Chapter 7, SphinxQL reference.

5.11. Multi-queries
===================

Multi-queries, or query batches, let you send multiple queries to Sphinx in
one go (more formally, one network request).

Two API methods that implement multi-query mechanism are AddQuery() and
RunQueries(). You can also run multiple queries with SphinxQL, see
Section 7.21, <<Multi-statement queries>>. (In fact, regular Query() call
is internally implemented as a single AddQuery() call immediately followed
by RunQueries() call.) AddQuery() captures the current state of all the
query settings set by previous API calls, and memorizes the query.
RunQueries() actually sends all the memorized queries, and returns multiple
result sets. There are no restrictions on the queries at all, except just
a sanity check on a number of queries in a single batch (see
Section 11.4.25, <<max_batch_queries>>).

Why use multi-queries? Generally, it all boils down to performance. First,
by sending requests to searchd in a batch instead of one by one, you always
save a bit by doing less network roundtrips. Second, and somewhat more
important, sending queries in a batch enables searchd to perform certain
internal optimizations. As new types of optimizations are being added over
time, it generally makes sense to pack all the queries into batches where
possible, so that simply upgrading Sphinx to a new version would
automatically enable new optimizations. In the case when there aren't any
possible batch optimizations to apply, queries will be processed one by one
internally.

Why (or rather when) not use multi-queries? Multi-queries requires all the
queries in a batch to be independent, and sometimes they aren't. That is,
sometimes query B is based on query A results, and so can only be set up
after executing query A. For instance, you might want to display results
from a secondary index if and only if there were no results found in
a primary index. Or maybe just specify offset into 2nd result set based on
the amount of matches in the 1st result set. In that case, you will have to
use separate queries (or separate batches).

As of 0.9.10, there are two major optimizations to be aware of: common
query optimization (available since 0.9.8); and common subtree optimization
(available since 0.9.10).

Common query optimization means that searchd will identify all those
queries in a batch where only the sorting and group-by settings differ, and
only perform searching once. For instance, if a batch consists of
3 queries, all of them are for "ipod nano", but 1st query requests top-10
results sorted by price, 2nd query groups by vendor ID and requests top-5
vendors sorted by rating, and 3rd query requests max price, full-text
search for "ipod nano" will only be performed once, and its results will be
reused to build 3 different result sets.

So-called faceted searching is a particularly important case that benefits
from this optimization. Indeed, faceted searching can be implemented by
running a number of queries, one to retrieve search results themselves, and
a few other ones with same full-text query but different group-by settings
to retrieve all the required groups of results (top-3 authors, top-5
vendors, etc). And as long as full-text query and filtering settings stay
the same, common query optimization will trigger, and greatly improve
performance.

Common subtree optimization is even more interesting. It lets searchd
exploit similarities between batched full-text queries. It identifies
common full-text query parts (subtress) in all queries, and caches them
between queries. For instance, look at the following query batch:

   | barack obama president
   | barack obama john mccain
   | barack obama speech

There's a common two-word part ("barack obama") that can be computed only
once, then cached and shared across the queries. And common subtree
optimization does just that. Per-query cache size is strictly controlled by
subtree_docs_cache and subtree_hits_cache directives (so that caching all
sxiteen gazillions of documents that match "i am" does not exhaust the RAM
and instantly kill your server).

Here's a code sample (in PHP) that fire the same query in 3 different
sorting modes:

   | require ( "sphinxapi.php" );
   | $cl = new SphinxClient ();
   | $cl->SetMatchMode ( SPH_MATCH_EXTENDED );
   | 
   | $cl->SetSortMode ( SPH_SORT_RELEVANCE );
   | $cl->AddQuery ( "the", "lj" );
   | $cl->SetSortMode ( SPH_SORT_EXTENDED, "published desc" );
   | $cl->AddQuery ( "the", "lj" );
   | $cl->SetSortMode ( SPH_SORT_EXTENDED, "published asc" );
   | $cl->AddQuery ( "the", "lj" );
   | $res = $cl->RunQueries();

How to tell whether the queries in the batch were actually optimized? If
they were, respective query log will have a "multiplier" field that
specifies how many queries were processed together:

   | [Sun Jul 12 15:18:17.000 2009] 0.040 sec x3 [ext/0/rel 747541 (0,20)] [lj] the
   | [Sun Jul 12 15:18:17.000 2009] 0.040 sec x3 [ext/0/ext 747541 (0,20)] [lj] the
   | [Sun Jul 12 15:18:17.000 2009] 0.040 sec x3 [ext/0/ext 747541 (0,20)] [lj] the

Note the "x3" field. It means that this query was optimized and processed
in a sub-batch of 3 queries. For reference, this is how the regular log
would look like if the queries were not batched:

   | [Sun Jul 12 15:18:17.062 2009] 0.059 sec [ext/0/rel 747541 (0,20)] [lj] the
   | [Sun Jul 12 15:18:17.156 2009] 0.091 sec [ext/0/ext 747541 (0,20)] [lj] the
   | [Sun Jul 12 15:18:17.250 2009] 0.092 sec [ext/0/ext 747541 (0,20)] [lj] the

Note how per-query time in multi-query case was improved by a factor of
1.5x to 2.3x, depending on a particular sorting mode. In fact, for both
common query and common subtree optimizations, there were reports of 3x and
even more improvements, and that's from production instances, not just
synthetic tests.

5.12. Collations
================

Introduced to Sphinx in version 2.0.1-beta to supplement string sorting,
collations essentially affect the string attribute comparisons. They
specify both the character set encoding and the strategy that Sphinx uses
to compare strings when doing ORDER BY or GROUP BY with a string attribute
involved.

String attributes are stored as is when indexing, and no character set or
language information is attached to them. That's okay as long as Sphinx
only needs to store and return the strings to the calling application
verbatim. But when you ask Sphinx to sort by a string value, that request
immediately becomes quite ambiguous.

First, single-byte (ASCII, or ISO-8859-1, or Windows-1251) strings need to
be processed differently that the UTF-8 ones that may encode every
character with a variable number of bytes. So we need to know what is the
character set type to interepret the raw bytes as meaningful characters
properly.

Second, we additionally need to know the language-specific string sorting
rules. For instance, when sorting according to US rules in en_US locale,
the accented character '&iuml;' (small letter i with diaeresis) should be
placed somewhere after 'z'. However, when sorting with French rules and
fr_FR locale in mind, it should be placed between 'i' and 'j'. And some
other set of rules might choose to ignore accents at all, allowing '&iuml;'
and 'i' to be mixed arbitrarily.

Third, but not least, we might need case-sensitive sorting in some
scenarios and case-insensitive sorting in some others.

Collations combine all of the above: the character set, the lanugage rules,
and the case sensitivity. Sphinx currently provides the following four
collations.

   1. libc_ci
   2. libc_cs
   3. utf8_general_ci
   4. binary

The first two collations rely on several standard C library (libc) calls
and can thus support any locale that is installed on your system. They
provide case-insensitive (_ci) and case-sensitive (_cs) comparisons
respectively. By default they will use C locale, effectively resorting to
bytewise comparisons. To change that, you need to specify a different
available locale using collation_libc_locale directive. The list of locales
available on your system can usually be obtained with the locale command:

   | $ locale -a
   | C
   | en_AG
   | en_AU.utf8
   | en_BW.utf8
   | en_CA.utf8
   | en_DK.utf8
   | en_GB.utf8
   | en_HK.utf8
   | en_IE.utf8
   | en_IN
   | en_NG
   | en_NZ.utf8
   | en_PH.utf8
   | en_SG.utf8
   | en_US.utf8
   | en_ZA.utf8
   | en_ZW.utf8
   | es_ES
   | fr_FR
   | POSIX
   | ru_RU.utf8
   | ru_UA.utf8

The specific list of the system locales may vary. Consult your OS
documentation to install additional needed locales.

utf8_general_ci and binary locales are built-in into Sphinx. The first one
is a generic collation for UTF-8 data (without any so-called language
tailoring); it should behave similar to utf8_general_ci collation in MySQL.
The second one is a simple bytewise comparison.

Collation can be overriden via SphinxQL on a per-session basis using SET
collation_connection statement. All subsequent SphinxQL queries will use
this collation. SphinxAPI and SphinxSE queries will use the server default
collation, as specified in collation_server configuration directive. Sphinx
currently defaults to libc_ci collation.

Collations should affect all string attribute comparisons, including those
within ORDER BY and GROUP BY, so differently ordered or grouped results can
be returned depending on the collation chosen.

5.13. User-defined functions (UDF)
==================================

Starting with 2.0.1-beta, Sphinx supports User-Defined Functions, or UDF
for short. They can be loaded and unloaded dynamically into searchd without
having to restart the daemon, and used in expressions when searching. UDF
features at a glance are as follows.

   * Functions can take integer (both 32-bit and 64-bit), float, string, or
     MVA arguments.
   * Functions can return integer or float values.
   * Functions can check the argument number, types, and names and raise
     errors.
   * Only simple functions (that is, non-aggregate ones) are currently
     supported.

User-defined functions need your OS to support dynamically loadable
libraries (aka shared objects). Most of the modern OSes are eligible,
including Linux, Windows, MacOS, Solaris, BSD and others. (The internal
testing has been done on Linux and Windows.) The UDF libraries must reside
in a directory specified by plugin_dir directive, and the server must be
configured to use workers = threads mode. Relative paths to the library
files are not allowed. Once the library is succesfully built and copied to
the trusted location, you can then dynamically install and deinstall the
functions using CREATE FUNCTION and DROP FUNCTION statements respectively.
A single library can contain multiple functions. A library gets loaded when
you first install a function from it, and unloaded when you deinstall all
the functions from that library.

The library functions that will implement a UDF visible to SQL statements
need to follow C calling convention, and a simple naming convention. Sphinx
source distribution provides a sample file, src/udfexample.c, that defines
a few simple functions showing how to work with integer, string, and MVA
arguments; you can use that one as a foundation for your new functions. It
includes the UDF interface header file, src/sphinxudf.h, that defines the
required types and structures. sphinxudf.h header is standalone, that is,
does not require any other parts of Sphinx source to compile.

Every function that you intend to use in your SELECT statements requires at
least two corresponding C/C++ functions: the initialization call, and the
function call itself. You can also optionally define the deinitialization
call if your function requires any post-query cleanup. (For instance, if
you were allocating any memory in either the initialization call or the
function calls.) Function names in SQL are case insensitive, C function
names are not. They need to be all lower-case. Mistakes in function name
prevent UDFs from loading. You also have to pay special attention to the
calling convention used when compiling, the list and the types of
arguments, and the return type of the main function call. Mistakes in
either are likely to crash the server, or result in unexpected results in
the best case. Last but not least, all functions need to be thread-safe.

Let's assume for the sake of example that your UDF name in SphinxQL will be
MYFUNC. The initialization, main, and deinitialization functions would then
need to be named as follows and take the following arguments:

   | /// initialization function
   | /// called once during query initialization
   | /// returns 0 on success
   | /// returns non-zero and fills error_message buffer on failure
   | int myfunc_init ( SPH_UDF_INIT * init, SPH_UDF_ARGS * args,
   |                   char * error_message );
   | 
   | /// main call function
   | /// returns the computed value
   | /// writes non-zero value into error_flag to indicate errors
   | RETURN_TYPE myfunc ( SPH_UDF_INIT * init, SPH_UDF_ARGS * args,
   |                      char * error_flag );
   | 
   | /// optional deinitialization function
   | /// called once to cleanup once query processing is done
   | void myfunc_deinit ( SPH_UDF_INIT * init );

The two mentioned structures, SPH_UDF_INIT and SPH_UDF_ARGS, are defined in
the src/sphinxudf.h interface header and documented there. RETURN_TYPE of
the main function must be one of the following:

   * int for the functions that return INT.
   * sphinx_int64_t for the functions that return BIGINT.
   * float for the functions that return FLOAT.

The calling sequence is as follows. myfunc_init() is called once when
initializing the query. It can return a non-zero code to indicate
a failure; in that case query is not executed, and the error message from
the error_message buffer is returned. Otherwise, myfunc() is be called for
every row, and a myfunc_deinit() is then called when the query ends.
myfunc() can indicate an error by writing a non-zero byte value to
error_flag, in that case, it will no more be called for subsequent rows,
and a default value of 0 will be substituted. Sphinx might or might not
choose to terminate such queries early, neither behavior is currently
guaranteed.

Chapter 6. Command line tools reference
=======================================

Table of Contents

6.1. indexer command reference
6.2. searchd command reference
6.3. search command reference
6.4. spelldump command reference
6.5. indextool command reference

As mentioned elsewhere, Sphinx is not a single program called 'sphinx', but
a collection of 4 separate programs which collectively form Sphinx. This
section covers these tools and how to use them.

6.1. indexer command reference
==============================

indexer is the first of the two principle tools as part of Sphinx. Invoked
from either the command line directly, or as part of a larger script,
indexer is solely responsible for gathering the data that will be
searchable.

The calling syntax for indexer is as follows:

   | indexer [OPTIONS] [indexname1 [indexname2 [...]]]

Essentially you would list the different possible indexes (that you would
later make available to search) in sphinx.conf, so when calling indexer, as
a minimum you need to be telling it what index (or indexes) you want to
index.

If sphinx.conf contained details on 2 indexes, mybigindex and mysmallindex,
you could do the following:

   | $ indexer mybigindex
   | $ indexer mysmallindex mybigindex

As part of the configuration file, sphinx.conf, you specify one or more
indexes for your data. You might call indexer to reindex one of them,
ad-hoc, or you can tell it to process all indexes - you are not limited to
calling just one, or all at once, you can always pick some combination of
the available indexes.

The majority of the options for indexer are given in the configuration
file, however there are some options you might need to specify on the
command line as well, as they can affect how the indexing operation is
performed. These options are:

   * --config <file> (-c <file> for short) tells indexer to use the given
     file as its configuration. Normally, it will look for sphinx.conf in
     the installation directory (e.g. /usr/local/sphinx/etc/sphinx.conf if
     installed into /usr/local/sphinx), followed by the current directory
     you are in when calling indexer from the shell. This is most of use in
     shared environments where the binary files are installed somewhere
     like /usr/local/sphinx/ but you want to provide users with the ability
     to make their own custom Sphinx set-ups, or if you want to run
     multiple instances on a single server. In cases like those you could
     allow them to create their own sphinx.conf files and pass them to
     indexer with this option. For example:

      | $ indexer --config /home/myuser/sphinx.conf myindex

   * --all tells indexer to update every index listed in sphinx.conf,
     instead of listing individual indexes. This would be useful in small
     configurations, or cron-type or maintenance jobs where the entire
     index set will get rebuilt each day, or week, or whatever period is
     best. Example usage:

      | $ indexer --config /home/myuser/sphinx.conf --all

   * --rotate is used for rotating indexes. Unless you have the situation
     where you can take the search function offline without troubling
     users, you will almost certainly need to keep search running whilst
     indexing new documents. --rotate creates a second index, parallel to
     the first (in the same place, simply including .new in the filenames).
     Once complete, indexer notifies searchd via sending the SIGHUP signal,
     and searchd will attempt to rename the indexes (renaming the existing
     ones to include .old and renaming the .new to replace them), and then
     start serving from the newer files. Depending on the setting of
     seamless_rotate, there may be a slight delay in being able to search
     the newer indexes. Example usage:

      | $ indexer --rotate --all

   * --quiet tells indexer not to output anything, unless there is an
     error. Again, most used for cron-type, or other script jobs where the
     output is irrelevant or unnecessary, except in the event of some kind
     of error. Example usage:

      | $ indexer --rotate --all --quiet

   * --noprogress does not display progress details as they occur; instead,
     the final status details (such as documents indexed, speed of indexing
     and so on are only reported at completion of indexing. In instances
     where the script is not being run on a console (or 'tty'), this will
     be on by default. Example usage:

      | $ indexer --rotate --all --noprogress

   * --buildstops <outputfile.text> <N> reviews the index source, as if it
     were indexing the data, and produces a list of the terms that are
     being indexed. In other words, it produces a list of all the
     searchable terms that are becoming part of the index. Note; it does
     not update the index in question, it simply processes the data 'as if'
     it were indexing, including running queries defined with sql_query_pre
     or sql_query_post. outputfile.txt will contain the list of words, one
     per line, sorted by frequency with most frequent first, and
     N specifies the maximum number of words that will be listed; if
     sufficiently large to encompass every word in the index, only that
     many words will be returned. Such a dictionary list could be used for
     client application features around "Did you mean..." functionality,
     usually in conjunction with --buildfreqs, below. Example:

      | $ indexer myindex --buildstops word_freq.txt 1000

     This would produce a document in the current directory, word_freq.txt
     with the 1,000 most common words in 'myindex', ordered by most common
     first. Note that the file will pertain to the last index indexed when
     specified with multiple indexes or --all (i.e. the last one listed in
     the configuration file)

   * --buildfreqs works with --buildstops (and is ignored if --buildstops
     is not specified). As --buildstops provides the list of words used
     within the index, --buildfreqs adds the quantity present in the index,
     which would be useful in establishing whether certain words should be
     considered stopwords if they are too prevalent. It will also help with
     developing "Did you mean..." features where you can how much more
     common a given word compared to another, similar one. Example:

      | $ indexer myindex --buildstops word_freq.txt 1000 --buildfreqs

     This would produce the word_freq.txt as above, however after each word
     would be the number of times it occurred in the index in question.

   * --merge <dst-index> <src-index> is used for physically merging indexes
     together, for example if you have a main+delta scheme, where the main
     index rarely changes, but the delta index is rebuilt frequently, and
     --merge would be used to combine the two. The operation moves from
     right to left - the contents of src-index get examined and physically
     combined with the contents of dst-index and the result is left in
     dst-index. In pseudo-code, it might be expressed as: dst-index +=
     src-index An example:

      | $ indexer --merge main delta --rotate

     In the above example, where the main is the master, rarely modified
     index, and delta is the less frequently modified one, you might use
     the above to call indexer to combine the contents of the delta into
     the main index and rotate the indexes.

   * --merge-dst-range <attr> <min> <max> runs the filter range given upon
     merging. Specifically, as the merge is applied to the destination
     index (as part of --merge, and is ignored if --merge is not
     specified), indexer will also filter the documents ending up in the
     destination index, and only documents will pass through the filter
     given will end up in the final index. This could be used for example,
     in an index where there is a 'deleted' attribute, where 0 means 'not
     deleted'. Such an index could be merged with:

      | $ indexer --merge main delta --merge-dst-range deleted 0 0

     Any documents marked as deleted (value 1) would be removed from the
     newly-merged destination index. It can be added several times to the
     command line, to add successive filters to the merge, all of which
     must be met in order for a document to become part of the final index.

   * --merge-killlists (and its shorter alias --merge-klists) changes the
     way kill lists are processed when merging indexes. By default, both
     kill lists get discarded after a merge. That supports the most typical
     main+delta merge scenario. With this option enabled, however, kill
     lists from both indexes get concatenated and stored into the
     destination index. Note that a source (delta) index kill list will be
     used to suppress rows from a destation (main) index at all times.
   * --dump-rows <FILE> dumps rows fetched by SQL source(s) into the
     specified file, in a MySQL compatible syntax. Resulting dumps are the
     exact representation of data as received by indexer and help to repeat
     indexing-time issues.
   * --verbose guarantees that every row that caused problems indexing
     (duplicate, zero, or missing document ID; or file field IO issues;
     etc) will be reported. By default, this option is off, and problem
     summaries may be reported instead.
   * --sighup-each is useful when you are rebuilding many big indexes, and
     want each one rotated into searchd as soon as possible. With
     --sighup-each, indexer will send a SIGHUP signal to searchd after
     succesfully completing the work on each index. (The default behavior
     is to send a single SIGHUP after all the indexes were built.)
   * --print-queries prints out SQL queries that indexer sends to the
     database, along with SQL connection and disconnection events. That is
     useful to diagnose and fix problems with SQL sources.
   * --print-queries prints out SQL queries that indexer sends to the
     database, along with SQL connection and disconnection events. That is
     useful to diagnose and fix problems with SQL sources.

6.2. searchd command reference
==============================

searchd is the second of the two principle tools as part of Sphinx. searchd
is the part of the system which actually handles searches; it functions as
a server and is responsible for receiving queries, processing them and
returning a dataset back to the different APIs for client applications.

Unlike indexer, searchd is not designed to be run either from a regular
script or command-line calling, but instead either as a daemon to be called
from init.d (on Unix/Linux type systems) or to be called as a service (on
Windows-type systems), so not all of the command line options will always
apply, and so will be build-dependent.

Calling searchd is simply a case of:

   | $ searchd [OPTIONS]

The options available to searchd on all builds are:

   * --help (-h for short) lists all of the parameters that can be called
     in your particular build of searchd.
   * --config <file> (-c <file> for short) tells searchd to use the given
     file as its configuration, just as with indexer above.
   * --stop is used to asynchronously stop searchd, using the details of
     the PID file as specified in the sphinx.conf file, so you may also
     need to confirm to searchd which configuration file to use with the
     --config option. NB, calling --stop will also make sure any changes
     applied to the indexes with UpdateAttributes() will be applied to the
     index files themselves. Example:

      | $ searchd --config /home/myuser/sphinx.conf --stop

   * --stopwait is used to synchronously stop searchd. --stop essentially
     tells the running instance to exit (by sending it a SIGTERM) and then
     immediately returns. --stopwait will also attempt to wait until the
     running searchd instance actually finishes the shutdown (eg. saves all
     the pending attribute changes) and exits. Example:

      | $ searchd --config /home/myuser/sphinx.conf --stopwait

     Possible exit codes are as follows:

      * 0 on success;
      * 1 if connection to running searchd daemon failed;
      * 2 if daemon reported an error during shutdown;
      * 3 if daemon crashed during shutdown.

   * --status command is used to query running searchd instance status,
     using the connection details from the (optionally) provided
     configuration file. It will try to connect to the running instance
     using the first configured UNIX socket or TCP port. On success, it
     will query for a number of status and performance counter values and
     print them. You can use Status() API call to access the very same
     counters from your application. Examples:

      | $ searchd --status
      | $ searchd --config /home/myuser/sphinx.conf --status

   * --pidfile is used to explicitly force using a PID file (where the
     searchd process number is stored) despite any other debugging options
     that say otherwise (for instance, --console). This is a debugging
     option.

      | $ searchd --console --pidfile

   * --console is used to force searchd into console mode; typically it
     will be running as a conventional server application, and will aim to
     dump information into the log files (as specified in sphinx.conf).
     Sometimes though, when debugging issues in the configuration or the
     daemon itself, or trying to diagnose hard-to-track-down problems, it
     may be easier to force it to dump information directly to the
     console/command line from which it is being called. Running in console
     mode also means that the process will not be forked (so searches are
     done in sequence) and logs will not be written to. (It should be noted
     that console mode is not the intended method for running searchd.) You
     can invoke it as such:

      | $ searchd --config /home/myuser/sphinx.conf --console

   * --logdebug, --logdebugv, and --logdebugvv options enable additional
     debug output in the daemon log. They differ by the logging verboseness
     level. These are debugging options, they pollute the log a lot, and
     thus they should not be normally enabled. (The normal use case for
     these is to enable them temporarily on request, to assist with some
     particularly complicated debugging session.)

   * --iostats is used in conjuction with the logging options (the
     query_log will need to have been activated in sphinx.conf) to provide
     more detailed information on a per-query basis as to the input/output
     operations carried out in the course of that query, with a slight
     performance hit and of course bigger logs. Further details are
     available under the query log format section. You might start searchd
     thus:

      | $ searchd --config /home/myuser/sphinx.conf --iostats

   * --cpustats is used to provide actual CPU time report (in addition to
     wall time) in both query log file (for every given query) and status
     report (aggregated). It depends on clock_gettime() system call and
     might therefore be unavailable on certain systems. You might start
     searchd thus:

      | $ searchd --config /home/myuser/sphinx.conf --cpustats

   * --port portnumber (-p for short) is used to specify the port that
     searchd should listen on, usually for debugging purposes. This will
     usually default to 9312, but sometimes you need to run it on
     a different port. Specifying it on the command line will override
     anything specified in the configuration file. The valid range is 0 to
     65535, but ports numbered 1024 and below usually require a privileged
     account in order to run. An example of usage:

      | $ searchd --port 9313

   * --listen ( address ":" port | port | path ) [ ":" protocol ] (or -l
     for short) Works as --port, but allow you to specify not only the
     port, but full path, as IP address and port, or Unix-domain socket
     path, that searchd will listen on. Otherwords, you can specify either
     an IP address (or hostname) and port number, or just a port number, or
     Unix socket path. If you specify port number but not the address,
     searchd will listen on all network interfaces. Unix path is identified
     by a leading slash. As the last param you can also specify a protocol
     handler (listener) to be used for connections on this socket.
     Supported protocol values are 'sphinx' (Sphinx 0.9.x API protocol) and
     'mysql41' (MySQL protocol used since 4.1 upto at least 5.1).
   * --index <index> (or -i <index> for short) forces this instance of
     searchd only to serve the specified index. Like --port, above, this is
     usually for debugging purposes; more long-term changes would generally
     be applied to the configuration file itself. Example usage:

      | $ searchd --index myindex

   * --strip-path strips the path names from all the file names referenced
     from the index (stopwords, wordforms, exceptions, etc). This is useful
     for picking up indexes built on another machine with possibly
     different path layouts.
   * --replay-flags=<OPTIONS> switch, added in version 2.0.2-beta, can be
     used to specify a list of extra binary log replay options. The
     supported options are:

      * accept-desc-timestamp, ignore descending transaction timestamps and
        replay such transactions anyway (the default behavior is to exit
        with an error).

   Example:

      | $ searchd --replay-flags=accept-desc-timestamp

There are some options for searchd that are specific to Windows platforms,
concerning handling as a service, are only be available on Windows
binaries.

Note that on Windows searchd will default to --console mode, unless you
install it as a service.

   * --install installs searchd as a service into the Microsoft Management
     Console (Control Panel / Administrative Tools / Services). Any other
     parameters specified on the command line, where --install is specified
     will also become part of the command line on future starts of the
     service. For example, as part of calling searchd, you will likely also
     need to specify the configuration file with --config, and you would do
     that as well as specifying --install. Once called, the usual
     start/stop facilities will become available via the management
     console, so any methods you could use for starting, stopping and
     restarting services would also apply to searchd. Example:

      | C:\WINDOWS\system32> C:\Sphinx\bin\searchd.exe --install
      |    --config C:\Sphinx\sphinx.conf

     If you wanted to have the I/O stats every time you started searchd,
     you would specify its option on the same line as the --install command
     thus:

      | C:\WINDOWS\system32> C:\Sphinx\bin\searchd.exe --install
      |    --config C:\Sphinx\sphinx.conf --iostats

   * --delete removes the service from the Microsoft Management Console and
     other places where services are registered, after previously installed
     with --install. Note, this does not uninstall the software or delete
     the indexes. It means the service will not be called from the services
     systems, and will not be started on the machine's next start. If
     currently running as a service, the current instance will not be
     terminated (until the next reboot, or searchd is called with --stop).
     If the service was installed with a custom name (with --servicename),
     the same name will need to be specified with --servicename when
     calling to uninstall. Example:

      | C:\WINDOWS\system32> C:\Sphinx\bin\searchd.exe --delete

   * --servicename <name> applies the given name to searchd when installing
     or deleting the service, as would appear in the Management Console;
     this will default to searchd, but if being deployed on servers where
     multiple administrators may log into the system, or a system with
     multiple searchd instances, a more descriptive name may be applicable.
     Note that unless combined with --install or --delete, this option does
     not do anything. Example:

      | C:\WINDOWS\system32> C:\Sphinx\bin\searchd.exe --install
      |    --config C:\Sphinx\sphinx.conf --servicename SphinxSearch

   * --ntservice is the option that is passed by the Management Console to
     searchd to invoke it as a service on Windows platforms. It would not
     normally be necessary to call this directly; this would normally be
     called by Windows when the service would be started, although if you
     wanted to call this as a regular service from the command-line (as the
     complement to --console) you could do so in theory.
   * --safetrace forces searchd to only use system backtrace() call in
     crash reports. In certain (rare) scenarios, this might be a "safer"
     way to get that report. This is a debugging option.
   * --nodetach switch (Linux only) tells searchd not to detach into
     background. This will also cause log entry to be printed out to
     console. Query processing operates as usual. This is a debugging
     option.

Last but not least, as every other daemon, searchd supports a number of
signals.

SIGTERM
   Initiates a clean shutdown. New queries will not be handled; but queries
   that are already started will not be forcibly interrupted.

SIGHUP
   Initiates index rotation. Depending on the value of seamless_rotate
   setting, new queries might be shortly stalled; clients will receive
   temporary errors.

SIGUSR1
   Forces reopen of searchd log and query log files, letting you implement
   log file rotation.

6.3. search command reference
=============================

search is one of the helper tools within the Sphinx package. Whereas
searchd is responsible for searches in a server-type environment, search is
aimed at testing the index from the command line, and testing the index
quickly without building a framework to make the connection to the server
and process its response.

Note: search is not intended to be deployed as part of a client
application; it is strongly recommended you do not write an interface to
search instead of searchd, and none of the bundled client APIs support this
method. (In any event, search will reload files each time, whereas searchd
will cache them in memory for performance.)

That said, many types of query that you could build in the APIs could also
be made with search, however for very complex searches it may be easier to
construct them using a small script and the corresponding API.
Additionally, some newer features may be available in the searchd system
that have not yet been brought into search.

The calling syntax for search is as follows:

   | search [OPTIONS] word1 [word2 [word3 [...]]]

When calling search, it is not necessary to have searchd running; simply
make sure that the account running the search program has read access to
the configuration file and the index files.

The default behaviour is to apply a search for word1 (AND word2 AND
word3... as specified) to all fields in all indexes as given in the
configuration file. If constructing the equivalent in the API, this would
be the equivalent to passing SPH_MATCH_ALL to SetMatchMode, and specifying
* as the indexes to query as part of Query.

There are many options available to search. Firstly, the general options:

   * --config <file> (-c <file> for short) tells search to use the given
     file as its configuration, just as with indexer above.
   * --index <index> (-i <index> for short) tells search to limit searching
     to the specified index only; normally it would attempt to search all
     of the physical indexes listed in sphinx.conf, not any distributed
     ones.
   * --stdin tells search to accept the query from the standard input,
     rather than the command line. This can be useful for testing purposes
     whereby you could feed input via pipes and from scripts.

Options for setting matches:

   * --any (-a for short) changes the matching mode to match any of the
     words as part of the query (word1 OR word2 OR word3). In the API this
     would be equivalent to passing SPH_MATCH_ANY to SetMatchMode.
   * --phrase (-p for short) changes the matching mode to match all of the
     words as part of the query, and do so in the phrase given (not
     including punctuation). In the API this would be equivalent to passing
     SPH_MATCH_PHRASE to SetMatchMode.
   * --boolean (-b for short) changes the matching mode to Boolean
     matching. Note if using Boolean syntax matching on the command line,
     you may need to escape the symbols (with a backslash) to avoid the
     shell/command line processor applying them, such as ampersands being
     escaped on a Unix/Linux system to avoid it forking to the search
     process, although this can be resolved by using --stdin, as below. In
     the API this would be equivalent to passing SPH_MATCH_BOOLEAN to
     SetMatchMode.
   * --ext (-e for short) changes the matching mode to extended matching
     which provides various text querying operators. In the API this would
     be equivalent to passing SPH_MATCH_EXTENDED to SetMatchMode.
   * --filter <attr> <v> (-f <attr> <v> for short) filters the results such
     that only documents where the attribute given (attr) matches the value
     given (v). For example, --filter deleted 0 only matches documents with
     an attribute called 'deleted' where its value is 0. You can also add
     multiple filters on the command line, by specifying multiple --filter
     multiple times, however if you apply a second filter to an attribute
     it will override the first defined filter.

Options for handling the results:

   * --limit <count> (-l count for short) limits the total number of
     matches back to the number given. If a 'group' is specified, this will
     be the number of grouped results. This defaults to 20 results if not
     specified (as do the APIs)
   * --offset <count> (-o <count> for short) offsets the result list by the
     number of places set by the count; this would be used for pagination
     through results, where if you have 20 results per 'page', the second
     page would begin at offset 20, the third page at offset 40, etc.
   * --group <attr> (-g <attr> for short) specifies that results should be
     grouped together based on the attribute specified. Like the GROUP BY
     clause in SQL, it will combine all results where the attribute given
     matches, and returns a set of results where each returned result is
     the best from each group. Unless otherwise specified, this will be the
     best match on relevance.
   * --groupsort <expr> (-gs <expr> for short) instructs that when results
     are grouped with --group, the expression given in <expr> shall
     determine the order of the groups. Note, this does not specify which
     is the best item within the group, only the order in which the groups
     themselves shall be returned.
   * --sortby <clause> (-s <clause> for short) specifies that results
     should be sorted in the order listed in <clause>. This allows you to
     specify the order you wish results to be presented in, ordering by
     different columns. For example, you could say --sortby "@weight DESC
     entrytime DESC" to sort entries first by weight (or relevance) and
     where two or more entries have the same weight, to then sort by the
     time with the highest time (newest) first. You will usually need to
     put the items in quotes (--sortby "@weight DESC") or use commas
     (--sortby @weight,DESC) to avoid the items being treated separately.
     Additionally, like the regular sorting modes, if --group (grouping) is
     being used, this will state how to establish the best match within
     each group.
   * --sortexpr expr (-S expr for short) specifies that the search results
     should be presented in an order determined by an arithmetic
     expression, stated in expr. For example: --sortexpr "@weight + (
     user_karma + ln(pageviews) )*0.1" (again noting that this will have to
     be quoted to avoid the shell dealing with the asterisk). Extended sort
     mode is discussed in more detail under the SPH_SORT_EXTENDED entry
     under the Sorting modes section of the manual.
   * --sort=date specifies that the results should be sorted by descending
     (i.e. most recent first) date. This requires that there is an
     attribute in the index that is set as a timestamp.
   * --rsort=date specifies that the results should be sorted by ascending
     (i.e. oldest first) date. This requires that there is an attribute in
     the index that is set as a timestamp.
   * --sort=ts specifies that the results should be sorted by timestamp in
     groups; it will return all of the documents whose timestamp is within
     the last hour, then sorted within that bracket for relevance. After,
     it would return the documents from the last day, sorted by relevance,
     then the last week and then the last month. It is discussed in more
     detail under the SPH_SORT_TIME_SEGMENTS entry under the Sorting modes
     section of the manual.

Other options:

   * --noinfo (-q for short) instructs search not to look-up data in your
     SQL database. Specifically, for debugging with MySQL and search, you
     can provide it with a query to look up the full article based on the
     returned document ID. It is explained in more detail under the
     sql_query_info directive.

6.4. spelldump command reference
================================

spelldump is one of the helper tools within the Sphinx package.

It is used to extract the contents of a dictionary file that uses ispell or
MySpell format, which can help build word lists for wordforms - all of the
possible forms are pre-built for you.

Its general usage is:

   | spelldump [options] <dictionary> <affix> [result] [locale-name]

The two main parameters are the dictionary's main file and its affix file;
usually these are named as [language-prefix].dict and [language-prefix].aff
and will be available with most common Linux distributions, as well as
various places online.

[result] specifies where the dictionary data should be output to, and
[locale-name] additionally specifies the locale details you wish to use.

There is an additional option, -c [file], which specifies a file for case
conversion details.

Examples of its usage are:

   | spelldump en.dict en.aff
   | spelldump ru.dict ru.aff ru.txt ru_RU.CP1251
   | spelldump ru.dict ru.aff ru.txt .1251

The results file will contain a list of all the words in the dictionary in
alphabetical order, output in the format of a wordforms file, which you can
use to customise for your specific circumstances. An example of the result
file:

   | zone > zone
   | zoned > zoned
   | zoning > zoning

6.5. indextool command reference
================================

indextool is one of the helper tools within the Sphinx package, introduced
in version 0.9.9-rc2. It is used to dump miscellaneous debug information
about the physical index. (Additional functionality such as index
verification is planned in the future, hence the indextool name rather than
just indexdump.) Its general usage is:

   | indextool <command> [options]

The only currently available option applies to all commands and lets you
specify the configuration file:

   * --config <file> (-c <file> for short) overrides the built-in config
     file names.

The commands are as follows:

   * --dumpheader FILENAME.sph quickly dumps the provided index header file
     without touching any other index files or even the configuration file.
     The report provides a breakdown of all the index settings, in
     particular the entire attribute and field list. Prior to 0.9.9-rc2,
     this command was present in CLI search utility.
   * --dumpconfig FILENAME.sph dumps the index definition from the given
     index header file in (almost) compliant sphinx.conf file format. Added
     in version 2.0.1-beta.
   * --dumpheader INDEXNAME dumps index header by index name with looking
     up the header path in the configuration file.
   * --dumpdocids INDEXNAME dumps document IDs by index name. It takes the
     data from attribute (.spa) file and therefore requires docinfo=extern
     to work.
   * --dumphitlist INDEXNAME KEYWORD dumps all the hits (occurences) of
     a given keyword in a given index, with keyword specified as text.
   * --dumphitlist INDEXNAME --wordid ID dumps all the hits (occurences) of
     a given keyword in a given index, with keyword specified as internal
     numeric ID.
   * --htmlstrip INDEXNAME filters stdin using HTML stripper settings for
     a given index, and prints the filtering results to stdout. Note that
     the settings will be taken from sphinx.conf, and not the index header.
   * --check INDEXNAME checks the index data files for consistency errors
     that might be introduced either by bugs in indexer and/or hardware
     faults. Starting with version 2.0.2-beta, --check also works on RT
     indexes, but checks disk chunks only.
   * --strip-path strips the path names from all the file names referenced
     from the index (stopwords, wordforms, exceptions, etc). This is useful
     for checking indexes built on another machine with possibly different
     path layouts.
   * --optimize-rt-klists optimizes the kill list memory use in the disk
     chunk of a given RT index. That is a one-off optimization intended for
     rather old RT indexes, created by development versions prior to
     1.10-beta release. As of 1.10-beta releases, this kill list
     optimization (purging) should happen automatically, and there should
     never be a need to use this option.

Chapter 7. SphinxQL reference
=============================

Table of Contents

7.1. SELECT syntax
7.2. SHOW META syntax
7.3. SHOW WARNINGS syntax
7.4. SHOW STATUS syntax
7.5. INSERT and REPLACE syntax
7.6. DELETE syntax
7.7. SET syntax
7.8. SET TRANSACTION syntax
7.9. BEGIN, COMMIT, and ROLLBACK syntax
7.10. CALL SNIPPETS syntax
7.11. CALL KEYWORDS syntax
7.12. SHOW TABLES syntax
7.13. DESCRIBE syntax
7.14. CREATE FUNCTION syntax
7.15. DROP FUNCTION syntax
7.16. SHOW VARIABLES syntax
7.17. SHOW COLLATION syntax
7.18. UPDATE syntax
7.19. ATTACH INDEX syntax
7.20. FLUSH RTINDEX syntax
7.21. Multi-statement queries
7.22. Comment syntax
7.23. List of SphinxQL reserved keywords
7.24. SphinxQL upgrade notes, version 2.0.1-beta

SphinxQL is our SQL dialect that exposes all of the search daemon
functionality using a standard SQL syntax with a few Sphinx-specific
extensions. Everything available via the SphinxAPI is also available
SphinxQL but not vice versa; for instance, writes into RT indexes are only
available via SphinxQL. This chapter documents supported SphinxQL
statements syntax.

7.1. SELECT syntax
==================

   | SELECT
   |     select_expr [, select_expr ...]
   |     FROM index [, index2 ...]
   |     [WHERE where_condition]
   |     [GROUP BY {col_name | expr_alias}]
   |     [WITHIN GROUP ORDER BY {col_name | expr_alias} {ASC | DESC}]
   |     [ORDER BY {col_name | expr_alias} {ASC | DESC} [, ...]]
   |     [LIMIT offset, row_count]
   |     [OPTION opt_name = opt_value [, ...]]

SELECT statement was introduced in version 0.9.9-rc2. It's syntax is based
upon regular SQL but adds several Sphinx-specific extensions and has a few
omissions (such as (currently) missing support for JOINs). Specifically,

   * Column list clause. Column names, arbitrary expressions, and star
     ('*') are all allowed (ie. SELECT @id, group_id*123+456 AS expr1 FROM
     test1 will work). Unlike in regular SQL, all computed expressions must
     be aliased with a valid identifier. Starting with version 2.0.1-beta,
     AS is optional. Special names such as @id and @weight should currently
     be used with leading at-sign. This at-sign requirement will be lifted
     in the future.
   * FROM clause. FROM clause should contain the list of indexes to search
     through. Unlike in regular SQL, comma means enumeration of full-text
     indexes as in Query() API call rather than JOIN. Index name should be
     according to the rules of a C identifier.
   * WHERE clause. This clause will map both to fulltext query and filters.
     Comparison operators (=, !=, <, >, <=, >=), IN, AND, NOT, and BETWEEN
     are all supported and map directly to filters. OR is not supported yet
     but will be in the future. MATCH('query') is supported and maps to
     fulltext query. Query will be interpreted according to full-text query
     language rules. There must be at most one MATCH() in the clause.
     Starting with version 2.0.1-beta, {col_name | expr_alias} [NOT] IN
     @uservar condition syntax is supported. (Refer to Section 7.7, <<SET
     syntax>> for a discussion of global user variables.)
   * GROUP BY clause. Currently only supports grouping by a single column.
     The column however can be a computed expression:

      | SELECT *, group_id*1000+article_type AS gkey FROM example GROUP BY gkey

     Aggregate functions (AVG(), MIN(), MAX(), SUM()) in column list clause
     are supported. Arguments to aggregate functions can be either plain
     attributes or arbitrary expressions. COUNT(*) is implicitly supported
     as using GROUP BY will add @count column to result set. Explicit
     support might be added in the future. COUNT(DISTINCT attr) is
     supported. Currently there can be at most one COUNT(DISTINCT) per
     query and an argument needs to be an attribute. Both current
     restrictions on COUNT(DISTINCT) might be lifted in the future.

      | SELECT *, AVG(price) AS avgprice, COUNT(DISTINCT storeid)
      | FROM products
      | WHERE MATCH('ipod')
      | GROUP BY vendorid

     Starting with 2.0.1-beta, GROUP BY on a string attribute is supported,
     with respect for current collation (see Section 5.12, <<Collations>>).

   * WITHIN GROUP ORDER BY clause. This is a Sphinx specific extension that
     lets you control how the best row within a group will to be selected.
     The syntax matches that of regular ORDER BY clause:

      | SELECT *, INTERVAL(posted,NOW()-7*86400,NOW()-86400) AS timeseg
      | FROM example WHERE MATCH('my search query')
      | GROUP BY siteid
      | WITHIN GROUP ORDER BY @weight DESC
      | ORDER BY timeseg DESC, @weight DESC

     Starting with 2.0.1-beta, WITHIN GROUP ORDER BY on a string attribute
     is supported, with respect for current collation (see Section 5.12,
     <<Collations>>).

   * ORDER BY clause. Unlike in regular SQL, only column names (not
     expressions) are allowed and explicit ASC and DESC are required. The
     columns however can be computed expressions:

      | SELECT *, @weight*10+docboost AS skey FROM example ORDER BY skey

     Starting with 2.0.1-beta, ORDER BY on a string attribute is supported,
     with respect for current collation (see Section 5.12, <<Collations>>).

     Starting with 2.0.2-beta, ORDER BY RAND() syntax is supported. Note
     that this syntax is actually going to randomize the weight values and
     then order matches by those randomized weights.

   * LIMIT clause. Both LIMIT N and LIMIT M,N forms are supported. Unlike
     in regular SQL (but like in Sphinx API), an implicit LIMIT 0,20 is
     present by default.
   * OPTION clause. This is a Sphinx specific extension that lets you
     control a number of per-query options. The syntax is:

      | OPTION <optionname>=<value> [ , ... ]

     Supported options and respectively allowed values are:

      * 'ranker' - any of 'proximity_bm25', 'bm25', 'none', 'wordcount',
        'proximity', 'matchany', or 'fieldmask'
      * 'max_matches' - integer (per-query max matches value)
      * 'cutoff' - integer (max found matches threshold)
      * 'max_query_time' - integer (max search time threshold, msec)
      * 'retry_count' - integer (distributed retries count)
      * 'retry_delay' - integer (distributed retry delay, msec)
      * 'field_weights' - a named integer list (per-field user weights for
        ranking)
      * 'index_weights' - a named integer list (per-index user weights for
        ranking)
      * 'reverse_scan' - 0 or 1, lets you control the order in which
        full-scan query processes the rows
      * 'comment' - string, user comment that gets copied to a query log
        file

   Example:

      | SELECT * FROM test WHERE MATCH('@title hello @body world')
      | OPTION ranker=bm25, max_matches=3000,
      |     field_weights=(title=10, body=3)

7.2. SHOW META syntax
=====================

   | SHOW META

SHOW META shows additional meta-information about the latest query such as
query time and keyword statistics:

   | mysql> SELECT * FROM test1 WHERE MATCH('test|one|two');
   | +------+--------+----------+------------+
   | | id   | weight | group_id | date_added |
   | +------+--------+----------+------------+
   | |    1 |   3563 |      456 | 1231721236 |
   | |    2 |   2563 |      123 | 1231721236 |
   | |    4 |   1480 |        2 | 1231721236 |
   | +------+--------+----------+------------+
   | 3 rows in set (0.01 sec)
   | 
   | mysql> SHOW META;
   | +---------------+-------+
   | | Variable_name | Value |
   | +---------------+-------+
   | | total         | 3     |
   | | total_found   | 3     |
   | | time          | 0.005 |
   | | keyword[0]    | test  |
   | | docs[0]       | 3     |
   | | hits[0]       | 5     |
   | | keyword[1]    | one   |
   | | docs[1]       | 1     |
   | | hits[1]       | 2     |
   | | keyword[2]    | two   |
   | | docs[2]       | 1     |
   | | hits[2]       | 2     |
   | +---------------+-------+
   | 12 rows in set (0.00 sec)

7.3. SHOW WARNINGS syntax
=========================

   | SHOW WARNINGS

SHOW WARNINGS statement, introduced in version 0.9.9-rc2, can be used to
retrieve the warning produced by the latest query. The error message will
be returned along with the query itself:

   | mysql> SELECT * FROM test1 WHERE MATCH('@@title hello') \G
   | ERROR 1064 (42000): index test1: syntax error, unexpected TOK_FIELDLIMIT
   | near '@title hello'
   | 
   | mysql> SELECT * FROM test1 WHERE MATCH('@title -hello') \G
   | ERROR 1064 (42000): index test1: query is non-computable (single NOT operator)
   | 
   | mysql> SELECT * FROM test1 WHERE MATCH('"test doc"/3') \G
   | *************************** 1. row ***************************
   |         id: 4
   |     weight: 2500
   |   group_id: 2
   | date_added: 1231721236
   | 1 row in set, 1 warning (0.00 sec)
   | 
   | mysql> SHOW WARNINGS \G
   | *************************** 1. row ***************************
   |   Level: warning
   |    Code: 1000
   | Message: quorum threshold too high (words=2, thresh=3); replacing quorum operator
   |          with AND operator
   | 1 row in set (0.00 sec)

7.4. SHOW STATUS syntax
=======================

SHOW STATUS, introduced in version 0.9.9-rc2, displays a number of useful
performance counters. IO and CPU counters will only be available if searchd
was started with --iostats and --cpustats switches respectively.

   | mysql> SHOW STATUS;
   | +--------------------+-------+
   | | Variable_name      | Value |
   | +--------------------+-------+
   | | uptime             | 216   |
   | | connections        | 3     |
   | | maxed_out          | 0     |
   | | command_search     | 0     |
   | | command_excerpt    | 0     |
   | | command_update     | 0     |
   | | command_keywords   | 0     |
   | | command_persist    | 0     |
   | | command_status     | 0     |
   | | agent_connect      | 0     |
   | | agent_retry        | 0     |
   | | queries            | 10    |
   | | dist_queries       | 0     |
   | | query_wall         | 0.075 |
   | | query_cpu          | OFF   |
   | | dist_wall          | 0.000 |
   | | dist_local         | 0.000 |
   | | dist_wait          | 0.000 |
   | | query_reads        | OFF   |
   | | query_readkb       | OFF   |
   | | query_readtime     | OFF   |
   | | avg_query_wall     | 0.007 |
   | | avg_query_cpu      | OFF   |
   | | avg_dist_wall      | 0.000 |
   | | avg_dist_local     | 0.000 |
   | | avg_dist_wait      | 0.000 |
   | | avg_query_reads    | OFF   |
   | | avg_query_readkb   | OFF   |
   | | avg_query_readtime | OFF   |
   | +--------------------+-------+
   | 29 rows in set (0.00 sec)

7.5. INSERT and REPLACE syntax
==============================

   | {INSERT | REPLACE} INTO index [(column, ...)]
   | 	VALUES (value, ...)
   | 	[, (...)]

INSERT statement, introduced in version 1.10-beta, is only supported for RT
indexes. It inserts new rows (documents) into an existing index, with the
provided column values.

ID column must be present in all cases. Rows with duplicate IDs will not be
overwritten by INSERT; use REPLACE to do that.

index is the name of RT index into which the new row(s) should be inserted.
The optional column names list lets you only explicitly specify values for
some of the columns present in the index. All the other columns will be
filled with their default values (0 for scalar types, empty string for text
types).

Expressions are not currently supported in INSERT and values should be
explicitly specified.

Multiple rows can be inserted using a single INSERT statement by providing
several comma-separated, parens-enclosed lists of rows values.

7.6. DELETE syntax
==================

   | DELETE FROM index WHERE {id = value | id IN (val1 [, val2 [, ...]])}

DELETE statement, introduced in version 1.10-beta, is only supported for RT
indexes. It deletes existing rows (documents) from an existing index based
on ID.

index is the name of RT index from which the row should be deleted. value
is the row ID to be deleted. Support for batch id IN (2,3,5) syntax was
added in version 2.0.1-beta.

Additional types of WHERE conditions (such as conditions on attributes,
etc) are planned, but not supported yet as of 1.10-beta.

7.7. SET syntax
===============

   | SET [GLOBAL] server_variable_name = value
   | SET GLOBAL @user_variable_name = (int_val1 [, int_val2, ...])
   | SET NAMES value
   | SET @@dummy_variable = ignored_value

SET statement, introduced in version 1.10-beta, modifies a variable value.
The variable names are case-insensitive. No variable value changes survive
server restart.

SET NAMES statement and SET @@variable_name syntax, both introduced in
version 2.0.2-beta, do nothing. They were implemented to maintain
compatibility with 3rd party MySQL client libraries, connectors, and
frameworks that may need to run this statement when connecting.

There are the following classes of the variables:

   1. per-session server variable (1.10-beta and above)
   2. global server variable (2.0.1-beta and above)
   3. global user variable (2.0.1-beta and above)

Global user variables are shared between concurrent sessions. Currently,
the only supported value type is the list of BIGINTs, and these variables
can only be used along with IN() for filtering purpose. The intended usage
scenario is uploading huge lists of values to searchd (once) and reusing
them (many times) later, saving on network overheads. Example:

   | // in session 1
   | mysql> SET GLOBAL @myfilter=(2,3,5,7,11,13);
   | Query OK, 0 rows affected (0.00 sec)
   | 
   | // later in session 2
   | mysql> SELECT * FROM test1 WHERE group_id IN @myfilter;
   | +------+--------+----------+------------+-----------------+------+
   | | id   | weight | group_id | date_added | title           | tag  |
   | +------+--------+----------+------------+-----------------+------+
   | |    3 |      1 |        2 | 1299338153 | another doc     | 15   |
   | |    4 |      1 |        2 | 1299338153 | doc number four | 7,40 |
   | +------+--------+----------+------------+-----------------+------+
   | 2 rows in set (0.02 sec)

Per-session and global server variables affect certain server settings in
the respective scope. Known per-session server variables are:

AUTOCOMMIT = {0 | 1}
   Whether any data modification statement should be implicitly wrapped by
   BEGIN and COMMIT. Introduced in version 1.10-beta.

COLLATION_CONNECTION = collation_name
   Selects the collation to be used for ORDER BY or GROUP BY on string
   values in the subsequent queries. Refer to Section 5.12, <<Collations>>
   for a list of known collation names. Introduced in version 2.0.1-beta.

CHARACTER_SET_RESULTS = charset_name
   Does nothing; a placeholder to support frameworks, clients, and
   connectors that attempt to automatically enforce a charset when
   connecting to a Sphinx server. Introduced in version 2.0.1-beta.

SQL_AUTO_IS_NULL = value
   Does nothing; a placeholder to support frameworks, clients, and
   connectors that attempt to automatically enforce a charset when
   connecting to a Sphinx server. Introduced in version 2.0.2-beta.

SQL_MODE = value
   Does nothing; a placeholder to support frameworks, clients, and
   connectors that attempt to automatically enforce a charset when
   connecting to a Sphinx server. Introduced in version 2.0.2-beta.

Known global server variables are:

QUERY_LOG_FORMAT = {plain | sphinxql}
   Changes the current log format. Introduced in version 2.0.1-beta.

LOG_LEVEL = {info | debug | debugv | debugvv}
   Changes the current log verboseness level. Introduced in version
   2.0.1-beta.

Examples:

   | mysql> SET autocommit=0;
   | Query OK, 0 rows affected (0.00 sec)
   | 
   | mysql> SET GLOBAL query_log_format=sphinxql;
   | Query OK, 0 rows affected (0.00 sec)

7.8. SET TRANSACTION syntax
===========================

   | SET TRANSACTION ISOLATION LEVEL { READ UNCOMMITTED
   | 	| READ COMMITTED
   | 	| REPEATABLE READ
   | 	| SERIALIZABLE }

SET TRANSACTION statement, introduced in version 2.0.2-beta, does nothing.
It was implemented to maintain compatibility with 3rd party MySQL client
libraries, connectors, and frameworks that may need to run this statement
when connecting.

Example:

   | mysql> SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
   | Query OK, 0 rows affected (0.00 sec)

7.9. BEGIN, COMMIT, and ROLLBACK syntax
=======================================

   | START TRANSACTION | BEGIN
   | COMMIT
   | ROLLBACK
   | SET AUTOCOMMIT = {0 | 1}

BEGIN, COMMIT, and ROLLBACK statements were introduced in version
1.10-beta. BEGIN statement (or its START TRANSACTION alias) forcibly
commits pending transaction, if any, and begins a new one. COMMIT statement
commits the current transaction, making all its changes permanent. ROLLBACK
statement rolls back the current transaction, canceling all its changes.
SET AUTOCOMMIT controls the autocommit mode in the active session.

AUTOCOMMIT is set to 1 by default, meaning that every statement that
perfoms any changes on any index is implicitly wrapped in BEGIN and COMMIT.

Transactions are limited to a single RT index, and also limited in size.
They are atomic, consistent, overly isolated, and durable. Overly isolated
means that the changes are not only invisible to the concurrent
transactions but even to the current session itself.

7.10. CALL SNIPPETS syntax
==========================

   | CALL SNIPPETS(data, index, query[, opt_value AS opt_name[, ...]])

CALL SNIPPETS statement, introduced in version 1.10-beta, builds a snippet
from provided data and query, using specified index settings.

data is the source data to extract a snippet from. It could be a single
string, or the list of the strings enclosed in curly brackets. index is the
name of the index from which to take the text processing settings. query is
the full-text query to build snippets for. Additional options are
documented in Section 8.7.1, <<BuildExcerpts>>. Usage example:

   | CALL SNIPPETS('this is my document text', 'test1', 'hello world',
   |     5 AS around, 200 AS limit);
   | CALL SNIPPETS(('this is my document text','this is my another text'), 'test1', 'hello world',
   |     5 AS around, 200 AS limit);
   | CALL SNIPPETS(('data/doc1.txt','data/doc2.txt','/home/sphinx/doc3.txt'), 'test1', 'hello world',
   |     5 AS around, 200 AS limit, 1 AS load_files);

7.11. CALL KEYWORDS syntax
==========================

   | CALL KEYWORDS(text, index, [hits])

CALL KEYWORDS statement, introduced in version 1.10-beta, splits text into
particular keywords. It returns tokenized and normalized forms of the
keywords, and, optionally, keyword statistics.

text is the text to break down to keywords. index is the name of the index
from which to take the text processing settings. hits is an optional
boolean parameter that specifies whether to return document and hit
occurrence statistics.

7.12. SHOW TABLES syntax
========================

   | SHOW TABLES

SHOW TABLES statement, introduced in version 2.0.1-beta, enumerates all
currently active indexes along with their types. As of 2.0.1-beta, existing
index types are local, distributed, and rt respectively. Example:

   | mysql> SHOW TABLES;
   | +-------+-------------+
   | | Index | Type        |
   | +-------+-------------+
   | | dist1 | distributed |
   | | rt    | rt          |
   | | test1 | local       |
   | | test2 | local       |
   | +-------+-------------+
   | 4 rows in set (0.00 sec)

7.13. DESCRIBE syntax
=====================

   | {DESC | DESCRIBE} index

DESCRIBE statement, introduced in version 2.0.1-beta, lists index columns
and their associated types. Columns are document ID, full-text fields, and
attributes. The order matches that in which fields and attributes are
expected by INSERT and REPLACE statements. As of 2.0.1-beta, column types
are field, integer, timestamp, ordinal, bool, float, bigint, string, and
mva. ID column will be typed either integer or bigint based on whether the
binaries were built with 32-bit or 64-bit document ID support. Example:

   | mysql> DESC rt;
   | +---------+---------+
   | | Field   | Type    |
   | +---------+---------+
   | | id      | integer |
   | | title   | field   |
   | | content | field   |
   | | gid     | integer |
   | +---------+---------+
   | 4 rows in set (0.00 sec)

7.14. CREATE FUNCTION syntax
============================

   | CREATE FUNCTION udf_name
   | 	RETURNS {INT | BIGINT | FLOAT}
   | 	SONAME 'udf_lib_file'

CREATE FUNCTION statement, introduced in version 2.0.1-beta, installs
a user-defined function (UDF) with the given name and type from the given
library file. The library file must reside in a trusted plugin_dir
directory. On success, the function is available for use in all subsequent
queries that the server receives. Example:

   | mysql> CREATE FUNCTION avgmva RETURNS INT SONAME 'udfexample.dll';
   | Query OK, 0 rows affected (0.03 sec)
   | 
   | mysql> SELECT *, AVGMVA(tag) AS q from test1;
   | +------+--------+---------+-----------+
   | | id   | weight | tag     | q         |
   | +------+--------+---------+-----------+
   | |    1 |      1 | 1,3,5,7 | 4.000000  |
   | |    2 |      1 | 2,4,6   | 4.000000  |
   | |    3 |      1 | 15      | 15.000000 |
   | |    4 |      1 | 7,40    | 23.500000 |
   | +------+--------+---------+-----------+

7.15. DROP FUNCTION syntax
==========================

   | DROP FUNCTION udf_name

DROP FUNCTION statement, introduced in version 2.0.1-beta, deinstalls
a user-defined function (UDF) with the given name. On success, the function
is no longer available for use in subsequent queries. Pending concurrent
queries will not be affected and the library unload, if necessary, will be
postponed until those queries complete. Example:

   | mysql> DROP FUNCTION avgmva;
   | Query OK, 0 rows affected (0.00 sec)

7.16. SHOW VARIABLES syntax
===========================

   | SHOW [{GLOBAL | SESSION}] VARIABLES

SHOW VARIABLES statement was added in version 2.0.1-beta to improve
compatibility with 3rd party MySQL connectors and frameworks that
automatically execute this statement.

In version 2.0.1-beta, it did nothing.

Starting from version 2.0.2-beta, it returns the current values of a few
server-wide variables. Also, support for GLOBAL and SESSION clauses was
added.

   | mysql> SHOW GLOBAL VARIABLES;
   | +----------------------+----------+
   | | Variable_name        | Value    |
   | +----------------------+----------+
   | | autocommit           | 1        |
   | | collation_connection | libc_ci  |
   | | query_log_format     | sphinxql |
   | | log_level            | info     |
   | +----------------------+----------+
   | 4 rows in set (0.00 sec)

7.17. SHOW COLLATION syntax
===========================

   | SHOW COLLATION

Added in version 2.0.1-beta, this is currently a placeholder query that
does nothing and reports success. That is in order to keep compatibility
with frameworks and connectors that automatically execute this statement.

   | mysql> SHOW COLLATION;
   | Query OK, 0 rows affected (0.00 sec)

7.18. UPDATE syntax
===================

   | UPDATE index SET col1 = newval1 [, ...] WHERE where_condition

UPDATE statement was added in version 2.0.1-beta. Multiple attributes and
values can be specified in a single statement. Both RT and disk indexes are
supported.

As of version 2.0.2-beta, all atributes types (int, bigint, float, MVA)
except for strings can be updated. Previously, some of the types were not
supported.

where_condition (also added in 2.0.2-beta) has the same syntax as in the
SELECT statement (see Section 7.1, <<SELECT syntax>> for details).

When assigning the out-of-range values to 32-bit attributes, they will be
trimmed to their lower 32 bits without a prompt. For example, if you try to
update the 32-bit unsigned int with a value of 4294967297, the value of
1 will actually be stored, because the lower 32 bits of 4294967297
(0x100000001 in hex) amount to 1 (0x00000001 in hex).

MVA values sets for updating (and also for INSERT or REPLACE, refer to
Section 7.5, <<INSERT and REPLACE syntax>>) must be specificed as
comma-separated lists in parentheses. To erase the MVA value, just assign
() to it.

   | mysql> UPDATE myindex SET enabled=0 WHERE id=123;
   | Query OK, 1 rows affected (0.00 sec)
   | 
   | mysql> UPDATE myindex
   |   SET bigattr=-100000000000,
   |     fattr=3465.23,
   |     mvattr1=(3,6,4),
   |     mvattr2=()
   |   WHERE MATCH('hehe') AND enabled=1;
   | Query OK, 148 rows affected (0.01 sec)

7.19. ATTACH INDEX syntax
=========================

   | ATTACH INDEX diskindex TO RTINDEX rtindex

ATTACH INDEX statement, added in version 2.0.2-beta, lets you move data
from a regular disk index to a RT index.

After a successful ATTACH, the data originally stored in the source disk
index becomes a part of the target RT index, and the source disk index
becomes unavailable (until the next rebuild). ATTACH does not result in any
index data changes. Basically, it just renames the files (making the source
index a new disk chunk of the target RT index), and updates the metadata.
So it is a generally quick operation which might (frequently) complete as
fast as under a second.

Note that when an index is attached to an empty RT index, the fields,
attributes, and text processing settings (tokenizer, wordforms, etc) from
the source index are copied over and take effect. The respective parts of
the RT index definition from the configuration file will be ignored.

As of 2.0.2-beta, ATTACH INDEX comes with a number of restrictions. Most
notably, the target RT index is currently required to be empty, making
ATTACH INDEX a one-time conversion operation only. Those restrictions may
be lifted in future releases, as we add the needed functionality to the RT
indexes. The complete list is as follows.

   * Target RT index needs to be empty.
   * Source disk index needs to have index_sp=0, boundary_step=0,
     stopword_step=1, dict=crc settings.
   * Source disk index needs to have an empty index_zones setting.

   | mysql> DESC rt;
   | +-----------+---------+
   | | Field     | Type    |
   | +-----------+---------+
   | | id        | integer |
   | | testfield | field   |
   | | testattr  | uint    |
   | +-----------+---------+
   | 3 rows in set (0.00 sec)
   | 
   | mysql> SELECT * FROM rt;
   | Empty set (0.00 sec)
   | 
   | mysql> SELECT * FROM disk WHERE MATCH('test');
   | +------+--------+----------+------------+
   | | id   | weight | group_id | date_added |
   | +------+--------+----------+------------+
   | |    1 |   1304 |        1 | 1313643256 |
   | |    2 |   1304 |        1 | 1313643256 |
   | |    3 |   1304 |        1 | 1313643256 |
   | |    4 |   1304 |        1 | 1313643256 |
   | +------+--------+----------+------------+
   | 4 rows in set (0.00 sec)
   | 
   | mysql> ATTACH INDEX disk TO RTINDEX rt;
   | Query OK, 0 rows affected (0.00 sec)
   | 
   | mysql> DESC rt;
   | +------------+-----------+
   | | Field      | Type      |
   | +------------+-----------+
   | | id         | integer   |
   | | title      | field     |
   | | content    | field     |
   | | group_id   | uint      |
   | | date_added | timestamp |
   | +------------+-----------+
   | 5 rows in set (0.00 sec)
   | 
   | mysql> SELECT * FROM rt WHERE MATCH('test');
   | +------+--------+----------+------------+
   | | id   | weight | group_id | date_added |
   | +------+--------+----------+------------+
   | |    1 |   1304 |        1 | 1313643256 |
   | |    2 |   1304 |        1 | 1313643256 |
   | |    3 |   1304 |        1 | 1313643256 |
   | |    4 |   1304 |        1 | 1313643256 |
   | +------+--------+----------+------------+
   | 4 rows in set (0.00 sec)
   | 
   | mysql> SELECT * FROM disk WHERE MATCH('test');
   | ERROR 1064 (42000): no enabled local indexes to search

7.20. FLUSH RTINDEX syntax
==========================

   | FLUSH RTINDEX rtindex

FLUSH RTINDEX statement, added in version 2.0.2-beta, forcibly flushes RT
index RAM chunk contents to disk.

Backing up a RT index is as simple as copying over its data files, followed
by the binary log. However, recovering from that backup means that all the
transactions in the log since the last successful RAM chunk write would
need to be replayed. Those writes normally happen either on a clean
shutdown, or periodically with a (big enough!) interval between writes
specified in rt_flush_period directive. So such a backup made at an
arbitrary point in time just might end up with way too much binary log data
to replay.

FLUSH RTINDEX forcibly writes the RAM chunk contents to disk, and also
causes the subsequent cleanup of (now-redundant) binary log files. Thus,
recovering from a backup made just after FLUSH RTINDEX should be almost
instant.

   | mysql> FLUSH RTINDEX rt;
   | Query OK, 0 rows affected (0.05 sec)

7.21. Multi-statement queries
=============================

Starting version 2.0.1-beta, SphinxQL supports multi-statement queries, or
batches. Possible inter-statement optimizations described in Section 5.11,
<<Multi-queries>> do apply to SphinxQL just as well. The batched queries
should be separated by a semicolon. Your MySQL client library needs to
support MySQL multi-query mechanism and multiple result set. For instance,
mysqli interface in PHP and DBI/DBD libraries in Perl are known to work.

Here's a PHP sample showing how to utilize mysqli interface with Sphinx.

   | <?php
   | 
   | $link = mysqli_connect ( "127.0.0.1", "root", "", "", 9306 );
   | if ( mysqli_connect_errno() )
   |     die ( "connect failed: " . mysqli_connect_error() );
   | 
   | $batch = "SELECT * FROM test1 ORDER BY group_id ASC;";
   | $batch .= "SELECT * FROM test1 ORDER BY group_id DESC";
   | 
   | if ( !mysqli_multi_query ( $link, $batch ) )
   |     die ( "query failed" );
   | 
   | do
   | {
   |     // fetch and print result set
   |     if ( $result = mysqli_store_result($link) )
   |     {
   |         while ( $row = mysqli_fetch_row($result) )
   |             printf ( "id=%s\n", $row[0] );
   |         mysqli_free_result($result);
   |     }
   | 
   |     // print divider
   |     if ( mysqli_more_results($link) )
   |         printf ( "------\n" );
   | 
   | } while ( mysqli_next_result($link) );

Its output with the sample test1 index included with Sphinx is as follows.

   | $ php test_multi.php
   | id=1
   | id=2
   | id=3
   | id=4
   | ------
   | id=3
   | id=4
   | id=1
   | id=2

The following statements can currently be used in a batch: SELECT, SHOW
WARNINGS, SHOW STATUS, and SHOW META. Arbitrary sequence of these
statements are allowed. The results sets returned should match those that
would be returned if the batched queries were sent one by one.

7.22. Comment syntax
====================

Since version 2.0.1-beta, SphinxQL supports C-style comment syntax.
Everything from an opening /* sequence to a closing */ sequence is ignored.
Comments can span multiple lines, can not nest, and should not get logged.
MySQL specific /*! ... */ comments are also currently ignored. (As the
comments support was rather added for better compatibility with mysqldump
produced dumps, rather than improving generaly query interoperability
between Sphinx and MySQL.)

   | SELECT /*! SQL_CALC_FOUND_ROWS */ col1 FROM table1 WHERE ...

7.23. List of SphinxQL reserved keywords
========================================

A complete alphabetical list of keywords that are currently reserved in
SphinxQL syntax (and therefore can not be used as identifiers).

   | AND
   | AS
   | ASC
   | AVG
   | BEGIN
   | BETWEEN
   | BY
   | CALL
   | COLLATION
   | COMMIT
   | COUNT
   | DELETE
   | DESC
   | DESCRIBE
   | DISTINCT
   | FALSE
   | FROM
   | GLOBAL
   | GROUP
   | ID
   | IN
   | INSERT
   | INTO
   | LIMIT
   | MATCH
   | MAX
   | META
   | MIN
   | NOT
   | NULL
   | OPTION
   | OR
   | ORDER
   | REPLACE
   | ROLLBACK
   | SELECT
   | SET
   | SHOW
   | START
   | STATUS
   | SUM
   | TABLES
   | TRANSACTION
   | TRUE
   | UPDATE
   | VALUES
   | VARIABLES
   | WARNINGS
   | WEIGHT
   | WHERE
   | WITHIN

7.24. SphinxQL upgrade notes, version 2.0.1-beta
================================================

This section only applies to existing applications that use SphinxQL
versions prior to 2.0.1-beta.

In previous versions, SphinxQL just wrapped around SphinxAPI and inherited
its magic columns and column set quirks. Essentially, SphinxQL queries
could return (slightly) different columns and in a (slightly) different
order than it was explicitly requested in the query. Namely, weight magic
column (which is not a real column in any index) was added at all times,
and GROUP BY related @count, @group, and @distinct magic columns were
conditionally added when grouping. Also, the order of columns (attributes)
in the result set was actually taken from the index rather than the query.
(So if you asked for columns C, B, A in your query but they were in the A,
B, C order in the index, they would have been returned in the A, B,
C order.)

In version 2.0.1-beta, we fixed that. SphinxQL is now more SQL compliant
(and will be further brought in as much compliance with standard SQL syntax
as possible). That is not yet a breaking change, because searchd now
supports compat_sphinxql_magics directive that flips between the old
"compatibility" mode and the new "compliance" mode. However, the
compatibility mode support is going to be removed in future, so it's
strongly advised to update SphinxQL applications and switch to the
compliance mode.

The important changes are as follows:

   * @ID magic name is deprecated in favor of ID. Document ID is considered
     an attribute.
   * WEIGHT is no longer implicitly returned, because it is not actually
     a column (an index attribute), but rather an internal function
     computed per each row (a match). You have to explicitly ask for it,
     using the WEIGHT() function. (The requirement to alias the result will
     be lifted in the next release.)

      | SELECT id, WEIGHT() w FROM myindex WHERE MATCH('test')

   * You can now use quoted reserved keywords as aliases. The quote
     character is backtick ("`", ASCII code 96 decimal, 60 hex). One
     particularly useful example would be returning weight column like the
     old mode:

      | SELECT id, WEIGHT() `weight` FROM myindex WHERE MATCH('test')

   * The column order is now different and should now match the one
     expliclitly defined in the query. So if you are accessing columns
     based on their position in the result set rather than the name (for
     instance, by using mysql_fetch_row() rather than mysql_fetch_assoc()
     in PHP), check and fix the order of columns in your queries.
   * SELECT * return the columns in index order, as it used to, including
     the ID column. However, SELECT * does not automatically return
     WEIGHT(). To update such queries in case you access columns by names,
     simply add it to the query:

      | SELECT *, WEIGHT() `weight` FROM myindex WHERE MATCH('test')

     Otherwise, i.e., in case you rely on column order, select ID, weight,
     and then other columns:

      | SELECT id, *, WEIGHT() `weight` FROM myindex WHERE MATCH('test')

   * Magic @count and @distinct attributes are no longer implicitly
     returned. You now have to explicitly ask for them when using GROUP BY.
     (Also note that you currently have to alias them; that requirement
     will be lifted in the future.)

      | SELECT gid, COUNT(*) q FROM myindex WHERE MATCH('test')
      | GROUP BY gid ORDER BY q DESC

Chapter 8. API reference
========================

Table of Contents

8.1. General API functions
   8.1.1. GetLastError
   8.1.2. GetLastWarning
   8.1.3. SetServer
   8.1.4. SetRetries
   8.1.5. SetConnectTimeout
   8.1.6. SetArrayResult
   8.1.7. IsConnectError

8.2. General query settings
   8.2.1. SetLimits
   8.2.2. SetMaxQueryTime
   8.2.3. SetOverride
   8.2.4. SetSelect

8.3. Full-text search query settings
   8.3.1. SetMatchMode
   8.3.2. SetRankingMode
   8.3.3. SetSortMode
   8.3.4. SetWeights
   8.3.5. SetFieldWeights
   8.3.6. SetIndexWeights

8.4. Result set filtering settings
   8.4.1. SetIDRange
   8.4.2. SetFilter
   8.4.3. SetFilterRange
   8.4.4. SetFilterFloatRange
   8.4.5. SetGeoAnchor

8.5. GROUP BY settings
   8.5.1. SetGroupBy
   8.5.2. SetGroupDistinct

8.6. Querying
   8.6.1. Query
   8.6.2. AddQuery
   8.6.3. RunQueries
   8.6.4. ResetFilters
   8.6.5. ResetGroupBy

8.7. Additional functionality
   8.7.1. BuildExcerpts
   8.7.2. UpdateAttributes
   8.7.3. BuildKeywords
   8.7.4. EscapeString
   8.7.5. Status
   8.7.6. FlushAttributes

8.8. Persistent connections
   8.8.1. Open
   8.8.2. Close

There is a number of native searchd client API implementations for Sphinx.
As of time of this writing, we officially support our own PHP, Python, and
Java implementations. There also are third party free, open-source API
implementations for Perl, Ruby, and C++.

The reference API implementation is in PHP, because (we believe) Sphinx is
most widely used with PHP than any other language. This reference
documentation is in turn based on reference PHP API, and all code samples
in this section will be given in PHP.

However, all other APIs provide the same methods and implement the very
same network protocol. Therefore the documentation does apply to them as
well. There might be minor differences as to the method naming conventions
or specific data structures used. But the provided functionality must not
differ across languages.

8.1. General API functions
==========================

8.1.1. GetLastError
-------------------

Prototype: function GetLastError()

Returns last error message, as a string, in human readable format. If there
were no errors during the previous API call, empty string is returned.

You should call it when any other function (such as Query()) fails
(typically, the failing function returns false). The returned string will
contain the error description.

The error message is not reset by this call; so you can safely call it
several times if needed.

8.1.2. GetLastWarning
---------------------

Prototype: function GetLastWarning ()

Returns last warning message, as a string, in human readable format. If
there were no warnings during the previous API call, empty string is
returned.

You should call it to verify whether your request (such as Query()) was
completed but with warnings. For instance, search query against
a distributed index might complete succesfully even if several remote
agents timed out. In that case, a warning message would be produced.

The warning message is not reset by this call; so you can safely call it
several times if needed.

8.1.3. SetServer
----------------

Prototype: function SetServer ( $host, $port )

Sets searchd host name and TCP port. All subsequent requests will use the
new host and port settings. Default host and port are 'localhost' and 9312,
respectively.

8.1.4. SetRetries
-----------------

Prototype: function SetRetries ( $count, $delay=0 )

Sets distributed retry count and delay.

On temporary failures searchd will attempt up to $count retries per agent.
$delay is the delay between the retries, in milliseconds. Retries are
disabled by default. Note that this call will not make the API itself retry
on temporary failure; it only tells searchd to do so. Currently, the list
of temporary failures includes all kinds of connect() failures and maxed
out (too busy) remote agents.

8.1.5. SetConnectTimeout
------------------------

Prototype: function SetConnectTimeout ( $timeout )

Sets the time allowed to spend connecting to the server before giving up.

Under some circumstances, the server can be delayed in responding, either
due to network delays, or a query backlog. In either instance, this allows
the client application programmer some degree of control over how their
program interacts with searchd when not available, and can ensure that the
client application does not fail due to exceeding the script execution
limits (especially in PHP).

In the event of a failure to connect, an appropriate error code should be
returned back to the application in order for application-level error
handling to advise the user.

8.1.6. SetArrayResult
---------------------

Prototype: function SetArrayResult ( $arrayresult )

PHP specific. Controls matches format in the search results set (whether
matches should be returned as an array or a hash).

$arrayresult argument must be boolean. If $arrayresult is false (the
default mode), matches will returned in PHP hash format with document IDs
as keys, and other information (weight, attributes) as values. If
$arrayresult is true, matches will be returned as a plain array with
complete per-match information including document ID.

Introduced along with GROUP BY support on MVA attributes. Group-by-MVA
result sets may contain duplicate document IDs. Thus they need to be
returned as plain arrays, because hashes will only keep one entry per
document ID.

8.1.7. IsConnectError
---------------------

Prototype: function IsConnectError ()

Checks whether the last error was a network error on API side, or a remote
error reported by searchd. Returns true if the last connection attempt to
searchd failed on API side, false otherwise (if the error was remote, or
there were no connection attempts at all). Introduced in version 0.9.9-rc1.

8.2. General query settings
===========================

8.2.1. SetLimits
----------------

Prototype: function SetLimits ( $offset, $limit, $max_matches=0, $cutoff=0
)

Sets offset into server-side result set ($offset) and amount of matches to
return to client starting from that offset ($limit). Can additionally
control maximum server-side result set size for current query
($max_matches) and the threshold amount of matches to stop searching at
($cutoff). All parameters must be non-negative integers.

First two parameters to SetLimits() are identical in behavior to MySQL
LIMIT clause. They instruct searchd to return at most $limit matches
starting from match number $offset. The default offset and limit settings
are 0 and 20, that is, to return first 20 matches.

max_matches setting controls how much matches searchd will keep in RAM
while searching. All matching documents will be normally processed, ranked,
filtered, and sorted even if max_matches is set to 1. But only best
N documents are stored in memory at any given moment for performance and
RAM usage reasons, and this setting controls that N. Note that there are
two places where max_matches limit is enforced. Per-query limit is
controlled by this API call, but there also is per-server limit controlled
by max_matches setting in the config file. To prevent RAM usage abuse,
server will not allow to set per-query limit higher than the per-server
limit.

You can't retrieve more than max_matches matches to the client application.
The default limit is set to 1000. Normally, you must not have to go over
this limit. One thousand records is enough to present to the end user. And
if you're thinking about pulling the results to application for further
sorting or filtering, that would be much more efficient if performed on
Sphinx side.

$cutoff setting is intended for advanced performance control. It tells
searchd to forcibly stop search query once $cutoff matches had been found
and processed.

8.2.2. SetMaxQueryTime
----------------------

Prototype: function SetMaxQueryTime ( $max_query_time )

Sets maximum search query time, in milliseconds. Parameter must be
a non-negative integer. Default valus is 0 which means "do not limit".

Similar to $cutoff setting from SetLimits(), but limits elapsed query time
instead of processed matches count. Local search queries will be stopped
once that much time has elapsed. Note that if you're performing a search
which queries several local indexes, this limit applies to each index
separately.

8.2.3. SetOverride
------------------

Prototype: function SetOverride ( $attrname, $attrtype, $values )

Sets temporary (per-query) per-document attribute value overrides. Only
supports scalar attributes. $values must be a hash that maps document IDs
to overridden attribute values. Introduced in version 0.9.9-rc1.

Override feature lets you "temporary" update attribute values for some
documents within a single query, leaving all other queries unaffected. This
might be useful for personalized data. For example, assume you're
implementing a personalized search function that wants to boost the posts
that the user's friends recommend. Such data is not just dynamic, but also
personal; so you can't simply put it in the index because you don't want
everyone's searches affected. Overrides, on the other hand, are local to
a single query and invisible to everyone else. So you can, say, setup
a "friends_weight" value for every document, defaulting to 0, then
temporary override it with 1 for documents 123, 456 and 789 (recommended by
exactly the friends of current user), and use that value when ranking.

8.2.4. SetSelect
----------------

Prototype: function SetSelect ( $clause )

Sets the select clause, listing specific attributes to fetch, and
expressions to compute and fetch. Clause syntax mimics SQL. Introduced in
version 0.9.9-rc1.

SetSelect() is very similar to the part of a typical SQL query between
SELECT and FROM. It lets you choose what attributes (columns) to fetch, and
also what expressions over the columns to compute and fetch. A certain
difference from SQL is that expressions must always be aliased to a correct
identifier (consisting of letters and digits) using 'AS' keyword. SQL also
lets you do that but does not require to. Sphinx enforces aliases so that
the computation results can always be returned under a "normal" name in the
result set, used in other clauses, etc.

Everything else is basically identical to SQL. Star ('*') is supported.
Functions are supported. Arbitrary amount of expressions is supported.
Computed expressions can be used for sorting, filtering, and grouping, just
as the regular attributes.

Starting with version 0.9.9-rc2, aggregate functions (AVG(), MIN(), MAX(),
SUM()) are supported when using GROUP BY.

Expression sorting (Section 5.6, <<SPH_SORT_EXPR mode>>) and geodistance
functions (Section 8.4.5, <<SetGeoAnchor>>) are now internally implemented
using this computed expressions mechanism, using magic names '@expr' and
'@geodist' respectively.

Example:

   | $cl->SetSelect ( "*, @weight+(user_karma+ln(pageviews))*0.1 AS myweight" );
   | $cl->SetSelect ( "exp_years, salary_gbp*{$gbp_usd_rate} AS salary_usd,
   |    IF(age>40,1,0) AS over40" );
   | $cl->SetSelect ( "*, AVG(price) AS avgprice" );

8.3. Full-text search query settings
====================================

8.3.1. SetMatchMode
-------------------

Prototype: function SetMatchMode ( $mode )

Sets full-text query matching mode, as described in Section 5.1, <<Matching
modes>>. Parameter must be a constant specifying one of the known modes.

WARNING: (PHP specific) you must not take the matching mode constant name
in quotes, that syntax specifies a string and is incorrect:

   | $cl->SetMatchMode ( "SPH_MATCH_ANY" ); // INCORRECT! will not work as expected
   | $cl->SetMatchMode ( SPH_MATCH_ANY ); // correct, works OK

8.3.2. SetRankingMode
---------------------

Prototype: function SetRankingMode ( $ranker, $rankexpr="" )

Sets ranking mode (aka ranker). Only available in SPH_MATCH_EXTENDED
matching mode. Parameter must be a constant specifying one of the known
rankers.

By default, in the EXTENDED matching mode Sphinx computes two factors which
contribute to the final match weight. The major part is a phrase proximity
value between the document text and the query. The minor part is so-called
BM25 statistical function, which varies from 0 to 1 depending on the
keyword frequency within document (more occurrences yield higher weight)
and within the whole index (more rare keywords yield higher weight).

However, in some cases you'd want to compute weight differently - or maybe
avoid computing it at all for performance reasons because you're sorting
the result set by something else anyway. This can be accomplished by
setting the appropriate ranking mode. The list of the modes is available in
Section 5.4, <<Search results ranking>>.

$rankexpr argument was added in version 2.0.2-beta. It lets you specify
a ranking formula to use with the expression based ranker, that is, when
$ranker is set to SPH_RANK_EXPR. In all other cases, $rankexpr is ignored.

8.3.3. SetSortMode
------------------

Prototype: function SetSortMode ( $mode, $sortby="" )

Set matches sorting mode, as described in Section 5.6, <<Sorting modes>>.
Parameter must be a constant specifying one of the known modes.

WARNING: (PHP specific) you must not take the matching mode constant name
in quotes, that syntax specifies a string and is incorrect:

   | $cl->SetSortMode ( "SPH_SORT_ATTR_DESC" ); // INCORRECT! will not work as expected
   | $cl->SetSortMode ( SPH_SORT_ATTR_ASC ); // correct, works OK

8.3.4. SetWeights
-----------------

Prototype: function SetWeights ( $weights )

Binds per-field weights in the order of appearance in the index.
DEPRECATED, use SetFieldWeights() instead.

8.3.5. SetFieldWeights
----------------------

Prototype: function SetFieldWeights ( $weights )

Binds per-field weights by name. Parameter must be a hash (associative
array) mapping string field names to integer weights.

Match ranking can be affected by per-field weights. For instance, see
Section 5.4, <<Search results ranking>> for an explanation how phrase
proximity ranking is affected. This call lets you specify what non-default
weights to assign to different full-text fields.

The weights must be positive 32-bit integers. The final weight will be
a 32-bit integer too. Default weight value is 1. Unknown field names will
be silently ignored.

There is no enforced limit on the maximum weight value at the moment.
However, beware that if you set it too high you can start hitting 32-bit
wraparound issues. For instance, if you set a weight of 10,000,000 and
search in extended mode, then maximum possible weight will be equal to 10
million (your weight) by 1 thousand (internal BM25 scaling factor, see
Section 5.4, <<Search results ranking>>) by 1 or more (phrase proximity
rank). The result is at least 10 billion that does not fit in 32 bits and
will be wrapped around, producing unexpected results.

8.3.6. SetIndexWeights
----------------------

Prototype: function SetIndexWeights ( $weights )

Sets per-index weights, and enables weighted summing of match weights
across different indexes. Parameter must be a hash (associative array)
mapping string index names to integer weights. Default is empty array that
means to disable weighting summing.

When a match with the same document ID is found in several different local
indexes, by default Sphinx simply chooses the match from the index
specified last in the query. This is to support searching through partially
overlapping index partitions.

However in some cases the indexes are not just partitions, and you might
want to sum the weights across the indexes instead of picking one.
SetIndexWeights() lets you do that. With summing enabled, final match
weight in result set will be computed as a sum of match weight coming from
the given index multiplied by respective per-index weight specified in this
call. Ie. if the document 123 is found in index A with the weight of 2, and
also in index B with the weight of 3, and you called SetIndexWeights (
array ( "A"=>100, "B"=>10 ) ), the final weight return to the client will
be 2*100+3*10 = 230.

8.4. Result set filtering settings
==================================

8.4.1. SetIDRange
-----------------

Prototype: function SetIDRange ( $min, $max )

Sets an accepted range of document IDs. Parameters must be integers.
Defaults are 0 and 0; that combination means to not limit by range.

After this call, only those records that have document ID between $min and
$max (including IDs exactly equal to $min or $max) will be matched.

8.4.2. SetFilter
----------------

Prototype: function SetFilter ( $attribute, $values, $exclude=false )

Adds new integer values set filter.

On this call, additional new filter is added to the existing list of
filters. $attribute must be a string with attribute name. $values must be
a plain array containing integer values. $exclude must be a boolean value;
it controls whether to accept the matching documents (default mode, when
$exclude is false) or reject them.

Only those documents where $attribute column value stored in the index
matches any of the values from $values array will be matched (or rejected,
if $exclude is true).

8.4.3. SetFilterRange
---------------------

Prototype: function SetFilterRange ( $attribute, $min, $max, $exclude=false
)

Adds new integer range filter.

On this call, additional new filter is added to the existing list of
filters. $attribute must be a string with attribute name. $min and $max
must be integers that define the acceptable attribute values range
(including the boundaries). $exclude must be a boolean value; it controls
whether to accept the matching documents (default mode, when $exclude is
false) or reject them.

Only those documents where $attribute column value stored in the index is
between $min and $max (including values that are exactly equal to $min or
$max) will be matched (or rejected, if $exclude is true).

8.4.4. SetFilterFloatRange
--------------------------

Prototype: function SetFilterFloatRange ( $attribute, $min, $max,
$exclude=false )

Adds new float range filter.

On this call, additional new filter is added to the existing list of
filters. $attribute must be a string with attribute name. $min and $max
must be floats that define the acceptable attribute values range (including
the boundaries). $exclude must be a boolean value; it controls whether to
accept the matching documents (default mode, when $exclude is false) or
reject them.

Only those documents where $attribute column value stored in the index is
between $min and $max (including values that are exactly equal to $min or
$max) will be matched (or rejected, if $exclude is true).

8.4.5. SetGeoAnchor
-------------------

Prototype: function SetGeoAnchor ( $attrlat, $attrlong, $lat, $long )

Sets anchor point for and geosphere distance (geodistance) calculations,
and enable them.

$attrlat and $attrlong must be strings that contain the names of latitude
and longitude attributes, respectively. $lat and $long are floats that
specify anchor point latitude and longitude, in radians.

Once an anchor point is set, you can use magic "@geodist" attribute name in
your filters and/or sorting expressions. Sphinx will compute geosphere
distance between the given anchor point and a point specified by latitude
and lognitude attributes from each full-text match, and attach this value
to the resulting match. The latitude and longitude values both in
SetGeoAnchor and the index attribute data are expected to be in radians.
The result will be returned in meters, so geodistance value of 1000.0 means
1 km. 1 mile is approximately 1609.344 meters.

8.5. GROUP BY settings
======================

8.5.1. SetGroupBy
-----------------

Prototype: function SetGroupBy ( $attribute, $func, $groupsort="@group
desc" )

Sets grouping attribute, function, and groups sorting mode; and enables
grouping (as described in Section 5.7, <<Grouping (clustering) search
results >>).

$attribute is a string that contains group-by attribute name. $func is
a constant that chooses a function applied to the attribute value in order
to compute group-by key. $groupsort is a clause that controls how the
groups will be sorted. Its syntax is similar to that described in
Section 5.6, <<SPH_SORT_EXTENDED mode>>.

Grouping feature is very similar in nature to GROUP BY clause from SQL.
Results produces by this function call are going to be the same as produced
by the following pseudo code:

   | SELECT ... GROUP BY $func($attribute) ORDER BY $groupsort

Note that it's $groupsort that affects the order of matches in the final
result set. Sorting mode (see Section 8.3.3, <<SetSortMode>>) affect the
ordering of matches within group, ie. what match will be selected as the
best one from the group. So you can for instance order the groups by
matches count and select the most relevant match within each group at the
same time.

Starting with version 0.9.9-rc2, aggregate functions (AVG(), MIN(), MAX(),
SUM()) are supported through SetSelect() API call when using GROUP BY.

Starting with version 2.0.1-beta, grouping on string attributes is
supported, with respect to current collation.

8.5.2. SetGroupDistinct
-----------------------

Prototype: function SetGroupDistinct ( $attribute )

Sets attribute name for per-group distinct values count calculations. Only
available for grouping queries.

$attribute is a string that contains the attribute name. For each group,
all values of this attribute will be stored (as RAM limits permit), then
the amount of distinct values will be calculated and returned to the
client. This feature is similar to COUNT(DISTINCT) clause in standard SQL;
so these Sphinx calls:

   | $cl->SetGroupBy ( "category", SPH_GROUPBY_ATTR, "@count desc" );
   | $cl->SetGroupDistinct ( "vendor" );

can be expressed using the following SQL clauses:

   | SELECT id, weight, all-attributes,
   | 	COUNT(DISTINCT vendor) AS @distinct,
   | 	COUNT(*) AS @count
   | FROM products
   | GROUP BY category
   | ORDER BY @count DESC

In the sample pseudo code shown just above, SetGroupDistinct() call
corresponds to COUNT(DISINCT vendor) clause only. GROUP BY, ORDER BY, and
COUNT(*) clauses are all an equivalent of SetGroupBy() settings. Both
queries will return one matching row for each category. In addition to
indexed attributes, matches will also contain total per-category matches
count, and the count of distinct vendor IDs within each category.

8.6. Querying
=============

8.6.1. Query
------------

Prototype: function Query ( $query, $index="*", $comment="" )

Connects to searchd server, runs given search query with current settings,
obtains and returns the result set.

$query is a query string. $index is an index name (or names) string.
Returns false and sets GetLastError() message on general error. Returns
search result set on success. Additionally, the contents of $comment are
sent to the query log, marked in square brackets, just before the search
terms, which can be very useful for debugging. Currently, the comment is
limited to 128 characters.

Default value for $index is "*" that means to query all local indexes.
Characters allowed in index names include Latin letters (a-z), numbers
(0-9), minus sign (-), and underscore (_); everything else is considered
a separator. Therefore, all of the following samples calls are valid and
will search the same two indexes:

   | $cl->Query ( "test query", "main delta" );
   | $cl->Query ( "test query", "main;delta" );
   | $cl->Query ( "test query", "main, delta" );

Index specification order matters. If document with identical IDs are found
in two or more indexes, weight and attribute values from the very last
matching index will be used for sorting and returning to client (unless
explicitly overridden with SetIndexWeights()). Therefore, in the example
above, matches from "delta" index will always win over matches from "main".

On success, Query() returns a result set that contains some of the found
matches (as requested by SetLimits()) and additional general per-query
statistics. The result set is a hash (PHP specific; other languages might
utilize other structures instead of hash) with the following keys and
values:

"matches":
   Hash which maps found document IDs to another small hash containing
   document weight and attribute values (or an array of the similar small
   hashes if SetArrayResult() was enabled).

"total":
   Total amount of matches retrieved on server (ie. to the server side
   result set) by this query. You can retrieve up to this amount of matches
   from server for this query text with current query settings.

"total_found":
   Total amount of matching documents in index (that were found and
   procesed on server).

"words":
   Hash which maps query keywords (case-folded, stemmed, and otherwise
   processed) to a small hash with per-keyword statitics ("docs", "hits").

"error":
   Query error message reported by searchd (string, human readable). Empty
   if there were no errors.

"warning":
   Query warning message reported by searchd (string, human readable).
   Empty if there were no warnings.

It should be noted that Query() carries out the same actions as AddQuery()
and RunQueries() without the intermediate steps; it is analoguous to
a single AddQuery() call, followed by a corresponding RunQueries(), then
returning the first array element of matches (from the first, and only,
query.)

8.6.2. AddQuery
---------------

Prototype: function AddQuery ( $query, $index="*", $comment="" )

Adds additional query with current settings to multi-query batch. $query is
a query string. $index is an index name (or names) string. Additionally if
provided, the contents of $comment are sent to the query log, marked in
square brackets, just before the search terms, which can be very useful for
debugging. Currently, this is limited to 128 characters. Returns index to
results array returned from RunQueries().

Batch queries (or multi-queries) enable searchd to perform internal
optimizations if possible. They also reduce network connection overheads
and search process creation overheads in all cases. They do not result in
any additional overheads compared to simple queries. Thus, if you run
several different queries from your web page, you should always consider
using multi-queries.

For instance, running the same full-text query but with different sorting
or group-by settings will enable searchd to perform expensive full-text
search and ranking operation only once, but compute multiple group-by
results from its output.

This can be a big saver when you need to display not just plain search
results but also some per-category counts, such as the amount of products
grouped by vendor. Without multi-query, you would have to run several
queries which perform essentially the same search and retrieve the same
matches, but create result sets differently. With multi-query, you simply
pass all these querys in a single batch and Sphinx optimizes the redundant
full-text search internally.

AddQuery() internally saves full current settings state along with the
query, and you can safely change them afterwards for subsequent AddQuery()
calls. Already added queries will not be affected; there's actually no way
to change them at all. Here's an example:

   | $cl->SetSortMode ( SPH_SORT_RELEVANCE );
   | $cl->AddQuery ( "hello world", "documents" );
   | 
   | $cl->SetSortMode ( SPH_SORT_ATTR_DESC, "price" );
   | $cl->AddQuery ( "ipod", "products" );
   | 
   | $cl->AddQuery ( "harry potter", "books" );
   | 
   | $results = $cl->RunQueries ();

With the code above, 1st query will search for "hello world" in "documents"
index and sort results by relevance, 2nd query will search for "ipod" in
"products" index and sort results by price, and 3rd query will search for
"harry potter" in "books" index while still sorting by price. Note that 2nd
SetSortMode() call does not affect the first query (because it's already
added) but affects both other subsequent queries.

Additionally, any filters set up before an AddQuery() will fall through to
subsequent queries. So, if SetFilter() is called before the first query,
the same filter will be in place for the second (and subsequent) queries
batched through AddQuery() unless you call ResetFilters() first.
Alternatively, you can add additional filters as well.

This would also be true for grouping options and sorting options; no
current sorting, filtering, and grouping settings are affected by this
call; so subsequent queries will reuse current query settings.

AddQuery() returns an index into an array of results that will be returned
from RunQueries() call. It is simply a sequentially increasing 0-based
integer, ie. first call will return 0, second will return 1, and so on.
Just a small helper so you won't have to track the indexes manualy if you
need then.

8.6.3. RunQueries
-----------------

Prototype: function RunQueries ()

Connect to searchd, runs a batch of all queries added using AddQuery(),
obtains and returns the result sets. Returns false and sets GetLastError()
message on general error (such as network I/O failure). Returns a plain
array of result sets on success.

Each result set in the returned array is exactly the same as the result set
returned from Query().

Note that the batch query request itself almost always succeds - unless
there's a network error, blocking index rotation in progress, or another
general failure which prevents the whole request from being processed.

However individual queries within the batch might very well fail. In this
case their respective result sets will contain non-empty "error" message,
but no matches or query statistics. In the extreme case all queries within
the batch could fail. There still will be no general error reported,
because API was able to succesfully connect to searchd, submit the batch,
and receive the results - but every result set will have a specific error
message.

8.6.4. ResetFilters
-------------------

Prototype: function ResetFilters ()

Clears all currently set filters.

This call is only normally required when using multi-queries. You might
want to set different filters for different queries in the batch. To do
that, you should call ResetFilters() and add new filters using the
respective calls.

8.6.5. ResetGroupBy
-------------------

Prototype: function ResetGroupBy ()

Clears all currently group-by settings, and disables group-by.

This call is only normally required when using multi-queries. You can
change individual group-by settings using SetGroupBy() and
SetGroupDistinct() calls, but you can not disable group-by using those
calls. ResetGroupBy() fully resets previous group-by settings and disables
group-by mode in the current state, so that subsequent AddQuery() calls can
perform non-grouping searches.

8.7. Additional functionality
=============================

8.7.1. BuildExcerpts
--------------------

Prototype: function BuildExcerpts ( $docs, $index, $words, $opts=array() )

Excerpts (snippets) builder function. Connects to searchd, asks it to
generate excerpts (snippets) from given documents, and returns the results.

$docs is a plain array of strings that carry the documents' contents.
$index is an index name string. Different settings (such as charset,
morphology, wordforms) from given index will be used. $words is a string
that contains the keywords to highlight. They will be processed with
respect to index settings. For instance, if English stemming is enabled in
the index, "shoes" will be highlighted even if keyword is "shoe". Starting
with version 0.9.9-rc1, keywords can contain wildcards, that work similarly
to star-syntax available in queries. $opts is a hash which contains
additional optional highlighting parameters:

"before_match":
   A string to insert before a keyword match. Starting with version
   1.10-beta, a %PASSAGE_ID% macro can be used in this string. The macro is
   replaced with an incrementing passage number within a current snippet.
   Numbering starts at 1 by default but can be overridden with
   "start_passage_id" option. In a multi-document call, %PASSAGE_ID% would
   restart at every given document. Default is "<b>".

"after_match":
   A string to insert after a keyword match. Starting with version
   1.10-beta, a %PASSAGE_ID% macro can be used in this string. Default is
   "</b>".

"chunk_separator":
   A string to insert between snippet chunks (passages). Default is
   " ... ".

"limit":
   Maximum snippet size, in symbols (codepoints). Integer, default is 256.

"around":
   How much words to pick around each matching keywords block. Integer,
   default is 5.

"exact_phrase":
   Whether to highlight exact query phrase matches only instead of
   individual keywords. Boolean, default is false.

"single_passage":
   Whether to extract single best passage only. Boolean, default is false.

"use_boundaries":
   Whether to additionaly break passages by phrase boundary characters, as
   configured in index settings with phrase_boundary directive. Boolean,
   default is false.

"weight_order":
   Whether to sort the extracted passages in order of relevance (decreasing
   weight), or in order of appearance in the document (increasing
   position). Boolean, default is false.

"query_mode":
   Added in version 1.10-beta. Whether to handle $words as a query in
   extended syntax, or as a bag of words (default behavior). For instance,
   in query mode ("one two" | "three four") will only highlight and include
   those occurrences "one two" or "three four" when the two words from each
   pair are adjacent to each other. In default mode, any single occurrence
   of "one", "two", "three", or "four" would be highlighted. Boolean,
   default is false.

"force_all_words":
   Added in version 1.10-beta. Ignores the snippet length limit until it
   includes all the keywords. Boolean, default is false.

"limit_passages":
   Added in version 1.10-beta. Limits the maximum number of passages that
   can be included into the snippet. Integer, default is 0 (no limit).

"limit_words":
   Added in version 1.10-beta. Limits the maximum number of keywords that
   can be included into the snippet. Integer, default is 0 (no limit).

"start_passage_id":
   Added in version 1.10-beta. Specifies the starting value of %PASSAGE_ID%
   macro (that gets detected and expanded in before_match, after_match
   strings). Integer, default is 1.

"load_files":
   Added in version 1.10-beta. Whether to handle $docs as data to extract
   snippets from (default behavior), or to treat it as file names, and load
   data from specified files on the server side. Starting with version
   2.0.1-beta, up to dist_threads worker threads per request will be
   created to parallelize the work when this flag is enabled. Boolean,
   default is false. Starting with version 2.0.2-beta, building of the
   snippets could be parallelized between remote agents. Just set the
   'dist_threads' param in the config to the value greater than 1, and then
   invoke the snippets generation over the distributed index, which contain
   only one(!) first(!) local agent and several remotes.

"load_files_scattered":
   Added in version 2.0.2-beta. It works only with distributed snippets
   generation with remote agents. The source files for snippets could be
   distributed among different agents, and the main daemon will merge
   together all non-erroneous results. So, if one agent of the distributed
   index has 'file1.txt', another has 'file2.txt' and you call for the
   snippets with both these files, the sphinx will merge results from the
   agents together, so you will get the snippets from both 'file1.txt' and
   'file2.txt'. Boolean, default is false.

   If the "load_files" is also set, the request will return the error in
   case if any of the files is not available anywhere. Otherwise (if
   "load_files" is not set) it will just return the empty strings for all
   absent files. The master instance reset this flag when distributes the
   snippets among agents. So, for agents the absence of a file is not
   critical error, but for the master it might be so. If you want to be
   sure that all snippets are actually created, set both
   "load_files_scattered" and "load_files". If the absense of some snippets
   caused by some agents is not critical for you - set just
   "load_files_scattered", leaving "load_files" not set.

"html_strip_mode":
   Added in version 1.10-beta. HTML stripping mode setting. Defaults to
   "index", which means that index settings will be used. The other values
   are "none" and "strip", that forcibly skip or apply stripping
   irregardless of index settings; and "retain", that retains HTML markup
   and protects it from highlighting. The "retain" mode can only be used
   when highlighting full documents and thus requires that no snippet size
   limits are set. String, allowed values are "none", "strip", "index", and
   "retain".

"allow_empty":
   Added in version 1.10-beta. Allows empty string to be returned as
   highlighting result when a snippet could not be generated (no keywords
   match, or no passages fit the limit). By default, the beginning of
   original text would be returned instead of an empty string. Boolean,
   default is false.

"passage_boundary":
   Added in version 2.0.1-beta. Ensures that passages do not cross
   a sentence, paragraph, or zone boundary (when used with an index that
   has the respective indexing settings enabled). String, allowed values
   are "sentence", "paragraph", and "zone".

"emit_zones":
   Added in version 2.0.1-beta. Emits an HTML tag with an enclosing zone
   name before each passage. Boolean, default is false.

Snippets extraction algorithm currently favors better passages (with closer
phrase matches), and then passages with keywords not yet in snippet.
Generally, it will try to highlight the best match with the query, and it
will also to highlight all the query keywords, as made possible by the
limtis. In case the document does not match the query, beginning of the
document trimmed down according to the limits will be return by default.
Starting with 1.10-beta, you can also return an empty snippet instead case
by setting "allow_empty" option to true.

Returns false on failure. Returns a plain array of strings with excerpts
(snippets) on success.

8.7.2. UpdateAttributes
-----------------------

Prototype: function UpdateAttributes ( $index, $attrs, $values )

Instantly updates given attribute values in given documents. Returns number
of actually updated documents (0 or more) on success, or -1 on failure.

$index is a name of the index (or indexes) to be updated. $attrs is a plain
array with string attribute names, listing attributes that are updated.
$values is a hash where key is document ID, and value is a plain array of
new attribute values.

$index can be either a single index name or a list, like in Query(). Unlike
Query(), wildcard is not allowed and all the indexes to update must be
specified explicitly. The list of indexes can include distributed index
names. Updates on distributed indexes will be pushed to all agents.

The updates only work with docinfo=extern storage strategy. They are very
fast because they're working fully in RAM, but they can also be made
persistent: updates are saved on disk on clean searchd shutdown initiated
by SIGTERM signal. With additional restrictions, updates are also possible
on MVA attributes; refer to mva_updates_pool directive for details.

Usage example:

   | $cl->UpdateAttributes ( "test1", array("group_id"), array(1=>array(456)) );
   | $cl->UpdateAttributes ( "products", array ( "price", "amount_in_stock" ),
   | 	array ( 1001=>array(123,5), 1002=>array(37,11), 1003=>(25,129) ) );

The first sample statement will update document 1 in index "test1", setting
"group_id" to 456. The second one will update documents 1001, 1002 and 1003
in index "products". For document 1001, the new price will be set to 123
and the new amount in stock to 5; for document 1002, the new price will be
37 and the new amount will be 11; etc.

8.7.3. BuildKeywords
--------------------

Prototype: function BuildKeywords ( $query, $index, $hits )

Extracts keywords from query using tokenizer settings for given index,
optionally with per-keyword occurrence statistics. Returns an array of
hashes with per-keyword information.

$query is a query to extract keywords from. $index is a name of the index
to get tokenizing settings and keyword occurrence statistics from. $hits is
a boolean flag that indicates whether keyword occurrence statistics are
required.

Usage example:

   | $keywords = $cl->BuildKeywords ( "this.is.my query", "test1", false );

8.7.4. EscapeString
-------------------

Prototype: function EscapeString ( $string )

Escapes characters that are treated as special operators by the query
language parser. Returns an escaped string.

$string is a string to escape.

This function might seem redundant because it's trivial to implement in any
calling application. However, as the set of special characters might change
over time, it makes sense to have an API call that is guaranteed to escape
all such characters at all times.

Usage example:

   | $escaped = $cl->EscapeString ( "escaping-sample@query/string" );

8.7.5. Status
-------------

Prototype: function Status ()

Queries searchd status, and returns an array of status variable name and
value pairs.

Usage example:

   | $status = $cl->Status ();
   | foreach ( $status as $row )
   | 	print join ( ": ", $row ) . "\n";

8.7.6. FlushAttributes
----------------------

Prototype: function FlushAttributes ()

Forces searchd to flush pending attribute updates to disk, and blocks until
completion. Returns a non-negative internal "flush tag" on success. Returns
-1 and sets an error message on error. Introduced in version 1.10-beta.

Attribute values updated using UpdateAttributes() API call are only kept in
RAM until a so-called flush (which writes the current, possibly updated
attribute values back to disk). FlushAttributes() call lets you enforce
a flush. The call will block until searchd finishes writing the data to
disk, which might take seconds or even minutes depending on the total data
size (.spa file size). All the currently updated indexes will be flushed.

Flush tag should be treated as an ever growing magic number that does not
mean anything. It's guaranteed to be non-negative. It is guaranteed to grow
over time, though not necessarily in a sequential fashion; for instance,
two calls that return 10 and then 1000 respectively are a valid situation.
If two calls to FlushAttrs() return the same tag, it means that there were
no actual attribute updates in between them, and therefore current flushed
state remained the same (for all indexes).

Usage example:

   | $status = $cl->FlushAttributes ();
   | if ( $status<0 )
   | 	print "ERROR: " . $cl->GetLastError(); 

8.8. Persistent connections
===========================

Persistent connections allow to use single network connection to run
multiple commands that would otherwise require reconnects.

8.8.1. Open
-----------

Prototype: function Open ()

Opens persistent connection to the server.

8.8.2. Close
------------

Prototype: function Close ()

Closes previously opened persistent connection.

Chapter 9. MySQL storage engine (SphinxSE)
==========================================

Table of Contents

9.1. SphinxSE overview
9.2. Installing SphinxSE
   9.2.1. Compiling MySQL 5.0.x with SphinxSE
   9.2.2. Compiling MySQL 5.1.x with SphinxSE
   9.2.3. Checking SphinxSE installation

9.3. Using SphinxSE
9.4. Building snippets (excerpts) via MySQL

9.1. SphinxSE overview
======================

SphinxSE is MySQL storage engine which can be compiled into MySQL server
5.x using its pluggable architecure. It is not available for MySQL 4.x
series. It also requires MySQL 5.0.22 or higher in 5.0.x series, or MySQL
5.1.12 or higher in 5.1.x series.

Despite the name, SphinxSE does not actually store any data itself. It is
actually a built-in client which allows MySQL server to talk to searchd,
run search queries, and obtain search results. All indexing and searching
happen outside MySQL.

Obvious SphinxSE applications include:

   * easier porting of MySQL FTS applications to Sphinx;
   * allowing Sphinx use with progamming languages for which native APIs
     are not available yet;
   * optimizations when additional Sphinx result set processing on MySQL
     side is required (eg. JOINs with original document tables, additional
     MySQL-side filtering, etc).

9.2. Installing SphinxSE
========================

You will need to obtain a copy of MySQL sources, prepare those, and then
recompile MySQL binary. MySQL sources (mysql-5.x.yy.tar.gz) could be
obtained from dev.mysql.com Web site.

For some MySQL versions, there are delta tarballs with already prepared
source versions available from Sphinx Web site. After unzipping those over
original sources MySQL would be ready to be configured and built with
Sphinx support.

If such tarball is not available, or does not work for you for any reason,
you would have to prepare sources manually. You will need to GNU Autotools
framework (autoconf, automake and libtool) installed to do that.

9.2.1. Compiling MySQL 5.0.x with SphinxSE
------------------------------------------

   1. copy sphinx.5.0.yy.diff patch file into MySQL sources directory and
      run

      | patch -p1 < sphinx.5.0.yy.diff

      If there's no .diff file exactly for the specific version you need to
      build, try applying .diff with closest version numbers. It is
      important that the patch should apply with no rejects.

   2. in MySQL sources directory, run

      | sh BUILD/autorun.sh

   3. in MySQL sources directory, create sql/sphinx directory in and copy
      all files in mysqlse directory from Sphinx sources there. Example:

      | cp -R /root/builds/sphinx-0.9.7/mysqlse /root/builds/mysql-5.0.24/sql/sphinx

   4. configure MySQL and enable Sphinx engine:

      | ./configure --with-sphinx-storage-engine

   5. build and install MySQL:

      | make
      | make install

9.2.2. Compiling MySQL 5.1.x with SphinxSE
------------------------------------------

   1. in MySQL sources directory, create storage/sphinx directory in and
      copy all files in mysqlse directory from Sphinx sources there.
      Example:

      | cp -R /root/builds/sphinx-0.9.7/mysqlse /root/builds/mysql-5.1.14/storage/sphinx

   2. in MySQL sources directory, run

      | sh BUILD/autorun.sh

   3. configure MySQL and enable Sphinx engine:

      | ./configure --with-plugins=sphinx

   4. build and install MySQL:

      | make
      | make install

9.2.3. Checking SphinxSE installation
-------------------------------------

To check whether SphinxSE has been succesfully compiled into MySQL, launch
newly built servers, run mysql client and issue SHOW ENGINES query. You
should see a list of all available engines. Sphinx should be present and
"Support" column should contain "YES":

   | mysql> show engines;
   | +------------+----------+-------------------------------------------------------------+
   | | Engine     | Support  | Comment                                                     |
   | +------------+----------+-------------------------------------------------------------+
   | | MyISAM     | DEFAULT  | Default engine as of MySQL 3.23 with great performance      |
   |   ...
   | | SPHINX     | YES      | Sphinx storage engine                                       |
   |   ...
   | +------------+----------+-------------------------------------------------------------+
   | 13 rows in set (0.00 sec)

9.3. Using SphinxSE
===================

To search via SphinxSE, you would need to create special ENGINE=SPHINX
"search table", and then SELECT from it with full text query put into WHERE
clause for query column.

Let's begin with an example create statement and search query:

   | CREATE TABLE t1
   | (
   |     id          INTEGER UNSIGNED NOT NULL,
   |     weight      INTEGER NOT NULL,
   |     query       VARCHAR(3072) NOT NULL,
   |     group_id    INTEGER,
   |     INDEX(query)
   | ) ENGINE=SPHINX CONNECTION="sphinx://localhost:9312/test";
   | 
   | SELECT * FROM t1 WHERE query='test it;mode=any';

First 3 columns of search table must have a types of INTEGER UNSINGED or
BIGINT for the 1st column (document id), INTEGER or BIGINT for the 2nd
column (match weight), and VARCHAR or TEXT for the 3rd column (your query),
respectively. This mapping is fixed; you can not omit any of these three
required columns, or move them around, or change types. Also, query column
must be indexed; all the others must be kept unindexed. Columns' names are
ignored so you can use arbitrary ones.

Additional columns must be either INTEGER, TIMESTAMP, BIGINT, VARCHAR, or
FLOAT. They will be bound to attributes provided in Sphinx result set by
name, so their names must match attribute names specified in sphinx.conf.
If there's no such attribute name in Sphinx search results, column will
have NULL values.

Special "virtual" attributes names can also be bound to SphinxSE columns.
_sph_ needs to be used instead of @ for that. For instance, to obtain the
values of @groupby, @count, or @distinct virtual attributes, use
_sph_groupby, _sph_count or _sph_distinct column names, respectively.

CONNECTION string parameter can be used to specify default searchd host,
port and indexes for queries issued using this table. If no connection
string is specified in CREATE TABLE, index name "*" (ie. search all
indexes) and localhost:9312 are assumed. Connection string syntax is as
follows:

   | CONNECTION="sphinx://HOST:PORT/INDEXNAME"

You can change the default connection string later:

   | ALTER TABLE t1 CONNECTION="sphinx://NEWHOST:NEWPORT/NEWINDEXNAME";

You can also override all these parameters per-query.

As seen in example, both query text and search options should be put into
WHERE clause on search query column (ie. 3rd column); the options are
separated by semicolons; and their names from values by equality sign. Any
number of options can be specified. Available options are:

   * query - query text;
   * mode - matching mode. Must be one of "all", "any", "phrase",
     "boolean", or "extended". Default is "all";
   * sort - match sorting mode. Must be one of "relevance", "attr_desc",
     "attr_asc", "time_segments", or "extended". In all modes besides
     "relevance" attribute name (or sorting clause for "extended") is also
     required after a colon:

      | ... WHERE query='test;sort=attr_asc:group_id';
      | ... WHERE query='test;sort=extended:@weight desc, group_id asc';

   * offset - offset into result set, default is 0;
   * limit - amount of matches to retrieve from result set, default is 20;
   * index - names of the indexes to search:

      | ... WHERE query='test;index=test1;';
      | ... WHERE query='test;index=test1,test2,test3;';

   * minid, maxid - min and max document ID to match;
   * weights - comma-separated list of weights to be assigned to Sphinx
     full-text fields:

      | ... WHERE query='test;weights=1,2,3;';

   * filter, !filter - comma-separated attribute name and a set of values
     to match:

      | # only include groups 1, 5 and 19
      | ... WHERE query='test;filter=group_id,1,5,19;';
      | 
      | # exclude groups 3 and 11
      | ... WHERE query='test;!filter=group_id,3,11;';

   * range, !range - comma-separated attribute name, min and max value to
     match:

      | # include groups from 3 to 7, inclusive
      | ... WHERE query='test;range=group_id,3,7;';
      | 
      | # exclude groups from 5 to 25
      | ... WHERE query='test;!range=group_id,5,25;';

   * maxmatches - per-query max matches value, as in max_matches parameter
     to SetLimits() API call:

      | ... WHERE query='test;maxmatches=2000;';

   * cutoff - maximum allowed matches, as in cutoff parameter to
     SetLimits() API call:

      | ... WHERE query='test;cutoff=10000;';

   * maxquerytime - maximum allowed query time (in milliseconds), as in
     SetMaxQueryTime() API call:

      | ... WHERE query='test;maxquerytime=1000;';

   * groupby - group-by function and attribute, corresponding to
     SetGroupBy() API call:

      | ... WHERE query='test;groupby=day:published_ts;';
      | ... WHERE query='test;groupby=attr:group_id;';

   * groupsort - group-by sorting clause:

      | ... WHERE query='test;groupsort=@count desc;';

   * distinct - an attribute to compute COUNT(DISTINCT) for when doing
     group-by, as in SetGroupDistinct() API call:

      | ... WHERE query='test;groupby=attr:country_id;distinct=site_id';

   * indexweights - comma-separated list of index names and weights to use
     when searching through several indexes:

      | ... WHERE query='test;indexweights=idx_exact,2,idx_stemmed,1;';

   * comment - a string to mark this query in query log (mapping to
     $comment parameter in Query() API call):

      | ... WHERE query='test;comment=marker001;';

   * select - a string with expressions to compute (mapping to SetSelect()
     API call):

      | ... WHERE query='test;select=2*a+3*b as myexpr;';

   * host, port - remote searchd host name and TCP port, respectively:

      | ... WHERE query='test;host=sphinx-test.loc;port=7312;';

   * ranker - a ranking function to use with "extended" matching mode, as
     in SetRankingMode() API call (the only mode that supports full query
     syntax). Known values are "proximity_bm25", "bm25", "none",
     "wordcount", "proximity", "matchany", "fieldmask"; and, starting with
     2.0.4-release, "expr:EXPRESSION" syntax to support expression-based
     ranker (where EXPRESSION should be replaced with your specific ranking
     formula):

      | ... WHERE query='test;mode=extended;ranker=bm25;';
      | ... WHERE query='test;mode=extended;ranker=expr:sum(lcs);';

   * geoanchor - geodistance anchor, as in SetGeoAnchor() API call. Takes
     4 parameters which are latitude and longiture attribute names, and
     anchor point coordinates respectively:

      | ... WHERE query='test;geoanchor=latattr,lonattr,0.123,0.456';

One very important note that it is much more efficient to allow Sphinx to
perform sorting, filtering and slicing the result set than to raise max
matches count and use WHERE, ORDER BY and LIMIT clauses on MySQL side. This
is for two reasons. First, Sphinx does a number of optimizations and
performs better than MySQL on these tasks. Second, less data would need to
be packed by searchd, transferred and unpacked by SphinxSE.

Starting with version 0.9.9-rc1, additional query info besides result set
could be retrieved with SHOW ENGINE SPHINX STATUS statement:

   | mysql> SHOW ENGINE SPHINX STATUS;
   | +--------+-------+-------------------------------------------------+
   | | Type   | Name  | Status                                          |
   | +--------+-------+-------------------------------------------------+
   | | SPHINX | stats | total: 25, total found: 25, time: 126, words: 2 | 
   | | SPHINX | words | sphinx:591:1256 soft:11076:15945                | 
   | +--------+-------+-------------------------------------------------+
   | 2 rows in set (0.00 sec)

This information can also be accessed through status variables. Note that
this method does not require super-user privileges.

   | mysql> SHOW STATUS LIKE 'sphinx_%';
   | +--------------------+----------------------------------+
   | | Variable_name      | Value                            |
   | +--------------------+----------------------------------+
   | | sphinx_total       | 25                               | 
   | | sphinx_total_found | 25                               | 
   | | sphinx_time        | 126                              | 
   | | sphinx_word_count  | 2                                | 
   | | sphinx_words       | sphinx:591:1256 soft:11076:15945 | 
   | +--------------------+----------------------------------+
   | 5 rows in set (0.00 sec)

You could perform JOINs on SphinxSE search table and tables using other
engines. Here's an example with "documents" from example.sql:

   | mysql> SELECT content, date_added FROM test.documents docs
   | -> JOIN t1 ON (docs.id=t1.id) 
   | -> WHERE query="one document;mode=any";
   | +-------------------------------------+---------------------+
   | | content                             | docdate             |
   | +-------------------------------------+---------------------+
   | | this is my test document number two | 2006-06-17 14:04:28 | 
   | | this is my test document number one | 2006-06-17 14:04:28 | 
   | +-------------------------------------+---------------------+
   | 2 rows in set (0.00 sec)
   | 
   | mysql> SHOW ENGINE SPHINX STATUS;
   | +--------+-------+---------------------------------------------+
   | | Type   | Name  | Status                                      |
   | +--------+-------+---------------------------------------------+
   | | SPHINX | stats | total: 2, total found: 2, time: 0, words: 2 | 
   | | SPHINX | words | one:1:2 document:2:2                        | 
   | +--------+-------+---------------------------------------------+
   | 2 rows in set (0.00 sec)

9.4. Building snippets (excerpts) via MySQL
===========================================

Starting with version 0.9.9-rc2, SphinxSE also includes a UDF function that
lets you create snippets through MySQL. The functionality is fully similar
to BuildExcerprts API call but accesible through MySQL+SphinxSE.

The binary that provides the UDF is named sphinx.so and should be
automatically built and installed to proper location along with SphinxSE
itself. If it does not get installed automatically for some reason, look
for sphinx.so in the build directory and copy it to the plugins directory
of your MySQL instance. After that, register the UDF using the following
statement:

   | CREATE FUNCTION sphinx_snippets RETURNS STRING SONAME 'sphinx.so';

Function name must be sphinx_snippets, you can not use an arbitrary name.
Function arguments are as follows:

Prototype: function sphinx_snippets ( document, index, words, [options] );

Document and words arguments can be either strings or table columns.
Options must be specified like this: 'value' AS option_name. For a list of
supported options, refer to BuildExcerprts() API call. The only
UDF-specific additional option is named 'sphinx' and lets you specify
searchd location (host and port).

Usage examples:

   | SELECT sphinx_snippets('hello world doc', 'main', 'world',
   |     'sphinx://192.168.1.1/' AS sphinx, true AS exact_phrase,
   |     '[b]' AS before_match, '[/b]' AS after_match)
   | FROM documents;
   | 
   | SELECT title, sphinx_snippets(text, 'index', 'mysql php') AS text
   |     FROM sphinx, documents
   |     WHERE query='mysql php' AND sphinx.id=documents.id;

Chapter 10. Reporting bugs
==========================

Unfortunately, Sphinx is not yet 100% bug free (even though I'm working
hard towards that), so you might occasionally run into some issues.

Reporting as much as possible about each bug is very important - because to
fix it, I need to be able either to reproduce and debug the bug, or to
deduce what's causing it from the information that you provide. So here are
some instructions on how to do that.

Build-time issues
=================

If Sphinx fails to build for some reason, please do the following:

   1. check that headers and libraries for your DBMS are properly installed
      (for instance, check that mysql-devel package is present);
   2. report Sphinx version and config file (be sure to remove the
      passwords!), MySQL (or PostgreSQL) configuration info, gcc version,
      OS version and CPU type (ie. x86, x86-64, PowerPC, etc):

      | mysql_config
      | gcc --version
      | uname -a

   3. report the error message which is produced by configure or gcc (it
      should be to include error message itself only, not the whole build
      log).

Run-time issues
===============

If Sphinx builds and runs, but there are any problems running it, please do
the following:

   1. describe the bug (ie. both the expected behavior and actual behavior)
      and all the steps necessary to reproduce it;
   2. include Sphinx version and config file (be sure to remove the
      passwords!), MySQL (or PostgreSQL) version, gcc version, OS version
      and CPU type (ie. x86, x86-64, PowerPC, etc):

      | mysql --version
      | gcc --version
      | uname -a

   3. build, install and run debug versions of all Sphinx programs (this is
      to enable a lot of additional internal checks, so-called assertions):

      | make distclean
      | ./configure --with-debug
      | make install
      | killall -TERM searchd

   4. reindex to check if any assertions are triggered (in this case, it's
      likely that the index is corrupted and causing problems);
   5. if the bug does not reproduce with debug versions, revert to
      non-debug and mention it in your report;
   6. if the bug could be easily reproduced with a small (1-100 record)
      part of your database, please provide a gzipped dump of that part;
   7. if the problem is related to searchd, include relevant entries from
      searchd.log and query.log in your bug report;
   8. if the problem is related to searchd, try running it in console mode
      and check if it dies with an assertion:

      | ./searchd --console

   9. if any program dies with an assertion, provide the assertion message.

Debugging assertions, crashes and hangups
=========================================

If any program dies with an assertion, crashes without an assertion or
hangs up, you would additionally need to generate a core dump and examine
it.

   1. enable core dumps. On most Linux systems, this is done using ulimit:

      | ulimit -c 32768

   2. run the program and try to reproduce the bug;
   3. if the program crashes (either with or without an assertion), find
      the core file in current directory (it should typically print out
      "Segmentation fault (core dumped)" message);
   4. if the program hangs, use kill -SEGV from another console to force it
      to exit and dump core:

      | kill -SEGV HANGED-PROCESS-ID

   5. use gdb to examine the core file and obtain a backtrace:

      | gdb ./CRASHED-PROGRAM-FILE-NAME CORE-DUMP-FILE-NAME
      | (gdb) bt
      | (gdb) quit

Note that HANGED-PROCESS-ID, CRASHED-PROGRAM-FILE-NAME and
CORE-DUMP-FILE-NAME must all be replaced with specific numbers and file
names. For example, hanged searchd debugging session would look like:

   | # kill -SEGV 12345
   | # ls *core*
   | core.12345
   | # gdb ./searchd core.12345
   | (gdb) bt
   | ...
   | (gdb) quit

Note that ulimit is not server-wide and only affects current shell session.
This means that you will not have to restore any server-wide limits - but
if you relogin, you will have to set ulimit again.

Core dumps should be placed in current working directory (and Sphinx
programs do not change it), so this is where you would look for them.

Please do not immediately remove the core file because there could be
additional helpful information which could be retrieved from it. You do not
need to send me this file (as the debug info there is closely tied to your
system) but I might need to ask you a few additional questions about it.

Chapter 11. sphinx.conf options reference
=========================================

Table of Contents

11.1. Data source configuration options
   11.1.1. type
   11.1.2. sql_host
   11.1.3. sql_port
   11.1.4. sql_user
   11.1.5. sql_pass
   11.1.6. sql_db
   11.1.7. sql_sock
   11.1.8. mysql_connect_flags
   11.1.9. mysql_ssl_cert, mysql_ssl_key, mysql_ssl_ca
   11.1.10. odbc_dsn
   11.1.11. sql_query_pre
   11.1.12. sql_query
   11.1.13. sql_joined_field
   11.1.14. sql_query_range
   11.1.15. sql_range_step
   11.1.16. sql_query_killlist
   11.1.17. sql_attr_uint
   11.1.18. sql_attr_bool
   11.1.19. sql_attr_bigint
   11.1.20. sql_attr_timestamp
   11.1.21. sql_attr_str2ordinal
   11.1.22. sql_attr_float
   11.1.23. sql_attr_multi
   11.1.24. sql_attr_string
   11.1.25. sql_attr_str2wordcount
   11.1.26. sql_column_buffers
   11.1.27. sql_field_string
   11.1.28. sql_field_str2wordcount
   11.1.29. sql_file_field
   11.1.30. sql_query_post
   11.1.31. sql_query_post_index
   11.1.32. sql_ranged_throttle
   11.1.33. sql_query_info
   11.1.34. xmlpipe_command
   11.1.35. xmlpipe_field
   11.1.36. xmlpipe_field_string
   11.1.37. xmlpipe_field_wordcount
   11.1.38. xmlpipe_attr_uint
   11.1.39. xmlpipe_attr_bigint
   11.1.40. xmlpipe_attr_bool
   11.1.41. xmlpipe_attr_timestamp
   11.1.42. xmlpipe_attr_str2ordinal
   11.1.43. xmlpipe_attr_float
   11.1.44. xmlpipe_attr_multi
   11.1.45. xmlpipe_attr_multi_64
   11.1.46. xmlpipe_attr_string
   11.1.47. xmlpipe_fixup_utf8
   11.1.48. mssql_winauth
   11.1.49. mssql_unicode
   11.1.50. unpack_zlib
   11.1.51. unpack_mysqlcompress
   11.1.52. unpack_mysqlcompress_maxsize

11.2. Index configuration options
   11.2.1. type
   11.2.2. source
   11.2.3. path
   11.2.4. docinfo
   11.2.5. mlock
   11.2.6. morphology
   11.2.7. dict
   11.2.8. index_sp
   11.2.9. index_zones
   11.2.10. min_stemming_len
   11.2.11. stopwords
   11.2.12. wordforms
   11.2.13. exceptions
   11.2.14. min_word_len
   11.2.15. charset_type
   11.2.16. charset_table
   11.2.17. ignore_chars
   11.2.18. min_prefix_len
   11.2.19. min_infix_len
   11.2.20. prefix_fields
   11.2.21. infix_fields
   11.2.22. enable_star
   11.2.23. ngram_len
   11.2.24. ngram_chars
   11.2.25. phrase_boundary
   11.2.26. phrase_boundary_step
   11.2.27. html_strip
   11.2.28. html_index_attrs
   11.2.29. html_remove_elements
   11.2.30. local
   11.2.31. agent
   11.2.32. agent_blackhole
   11.2.33. agent_connect_timeout
   11.2.34. agent_query_timeout
   11.2.35. preopen
   11.2.36. ondisk_dict
   11.2.37. inplace_enable
   11.2.38. inplace_hit_gap
   11.2.39. inplace_docinfo_gap
   11.2.40. inplace_reloc_factor
   11.2.41. inplace_write_factor
   11.2.42. index_exact_words
   11.2.43. overshort_step
   11.2.44. stopword_step
   11.2.45. hitless_words
   11.2.46. expand_keywords
   11.2.47. blend_chars
   11.2.48. blend_mode
   11.2.49. rt_mem_limit
   11.2.50. rt_field
   11.2.51. rt_attr_uint
   11.2.52. rt_attr_bigint
   11.2.53. rt_attr_float
   11.2.54. rt_attr_multi
   11.2.55. rt_attr_multi_64
   11.2.56. rt_attr_timestamp
   11.2.57. rt_attr_string

11.3. indexer program configuration options
   11.3.1. mem_limit
   11.3.2. max_iops
   11.3.3. max_iosize
   11.3.4. max_xmlpipe2_field
   11.3.5. write_buffer
   11.3.6. max_file_field_buffer
   11.3.7. on_file_field_error

11.4. searchd program configuration options
   11.4.1. listen
   11.4.2. address
   11.4.3. port
   11.4.4. log
   11.4.5. query_log
   11.4.6. query_log_format
   11.4.7. read_timeout
   11.4.8. client_timeout
   11.4.9. max_children
   11.4.10. pid_file
   11.4.11. max_matches
   11.4.12. seamless_rotate
   11.4.13. preopen_indexes
   11.4.14. unlink_old
   11.4.15. attr_flush_period
   11.4.16. ondisk_dict_default
   11.4.17. max_packet_size
   11.4.18. mva_updates_pool
   11.4.19. crash_log_path
   11.4.20. max_filters
   11.4.21. max_filter_values
   11.4.22. listen_backlog
   11.4.23. read_buffer
   11.4.24. read_unhinted
   11.4.25. max_batch_queries
   11.4.26. subtree_docs_cache
   11.4.27. subtree_hits_cache
   11.4.28. workers
   11.4.29. dist_threads
   11.4.30. binlog_path
   11.4.31. binlog_flush
   11.4.32. binlog_max_log_size
   11.4.33. collation_server
   11.4.34. collation_libc_locale
   11.4.35. plugin_dir
   11.4.36. mysql_version_string
   11.4.37. rt_flush_period
   11.4.38. thread_stack
   11.4.39. expansion_limit
   11.4.40. compat_sphinxql_magics
   11.4.41. watchdog
   11.4.42. prefork_rotation_throttle

11.1. Data source configuration options
=======================================

11.1.1. type
------------

Data source type. Mandatory, no default value. Known types are mysql,
pgsql, mssql, xmlpipe and xmlpipe2, and odbc.

All other per-source options depend on source type selected by this option.
Names of the options used for SQL sources (ie. MySQL, PostgreSQL, MS SQL)
start with "sql_"; names of the ones used for xmlpipe and xmlpipe2 start
with "xmlpipe_". All source types except xmlpipe are conditional; they
might or might not be supported depending on your build settings, installed
client libraries, etc. mssql type is currently only available on Windows.
odbc type is available both on Windows natively and on Linux through
UnixODBC library.

Example:

   | type = mysql

11.1.2. sql_host
----------------

SQL server host to connect to. Mandatory, no default value. Applies to SQL
source types (mysql, pgsql, mssql) only.

In the simplest case when Sphinx resides on the same host with your MySQL
or PostgreSQL installation, you would simply specify "localhost". Note that
MySQL client library chooses whether to connect over TCP/IP or over UNIX
socket based on the host name. Specifically "localhost" will force it to
use UNIX socket (this is the default and generally recommended mode) and
"127.0.0.1" will force TCP/IP usage. Refer to MySQL manual for more
details.

Example:

   | sql_host = localhost

11.1.3. sql_port
----------------

SQL server IP port to connect to. Optional, default is 3306 for mysql
source type and 5432 for pgsql type. Applies to SQL source types (mysql,
pgsql, mssql) only. Note that it depends on sql_host setting whether this
value will actually be used.

Example:

   | sql_port = 3306

11.1.4. sql_user
----------------

SQL user to use when connecting to sql_host. Mandatory, no default value.
Applies to SQL source types (mysql, pgsql, mssql) only.

Example:

   | sql_user = test

11.1.5. sql_pass
----------------

SQL user password to use when connecting to sql_host. Mandatory, no default
value. Applies to SQL source types (mysql, pgsql, mssql) only.

Example:

   | sql_pass = mysecretpassword

11.1.6. sql_db
--------------

SQL database (in MySQL terms) to use after the connection and perform
further queries within. Mandatory, no default value. Applies to SQL source
types (mysql, pgsql, mssql) only.

Example:

   | sql_db = test

11.1.7. sql_sock
----------------

UNIX socket name to connect to for local SQL servers. Optional, default
value is empty (use client library default settings). Applies to SQL source
types (mysql, pgsql, mssql) only.

On Linux, it would typically be /var/lib/mysql/mysql.sock. On FreeBSD, it
would typically be /tmp/mysql.sock. Note that it depends on sql_host
setting whether this value will actually be used.

Example:

   | sql_sock = /tmp/mysql.sock

11.1.8. mysql_connect_flags
---------------------------

MySQL client connection flags. Optional, default value is 0 (do not set any
flags). Applies to mysql source type only.

This option must contain an integer value with the sum of the flags. The
value will be passed to mysql_real_connect() verbatim. The flags are
enumerated in mysql_com.h include file. Flags that are especially
interesting in regard to indexing, with their respective values, are as
follows:

   * CLIENT_COMPRESS = 32; can use compression protocol
   * CLIENT_SSL = 2048; switch to SSL after handshake
   * CLIENT_SECURE_CONNECTION = 32768; new 4.1 authentication

For instance, you can specify 2080 (2048+32) to use both compression and
SSL, or 32768 to use new authentication only. Initially, this option was
introduced to be able to use compression when the indexer and mysqld are on
different hosts. Compression on 1 Gbps links is most likely to hurt
indexing time though it reduces network traffic, both in theory and in
practice. However, enabling compression on 100 Mbps links may improve
indexing time significantly (upto 20-30% of the total indexing time
improvement was reported). Your mileage may vary.

Example:

   | mysql_connect_flags = 32 # enable compression

11.1.9. mysql_ssl_cert, mysql_ssl_key, mysql_ssl_ca
---------------------------------------------------

SSL certificate settings to use for connecting to MySQL server. Optional,
default values are empty strings (do not use SSL). Applies to mysql source
type only.

These directives let you set up secure SSL connection between indexer and
MySQL. The details on creating the certificates and setting up MySQL server
can be found in MySQL documentation.

Example:

   | mysql_ssl_cert = /etc/ssl/client-cert.pem
   | mysql_ssl_key = /etc/ssl/client-key.pem
   | mysql_ssl_ca = /etc/ssl/cacert.pem

11.1.10. odbc_dsn
-----------------

ODBC DSN to connect to. Mandatory, no default value. Applies to odbc source
type only.

ODBC DSN (Data Source Name) specifies the credentials (host, user,
password, etc) to use when connecting to ODBC data source. The format
depends on specific ODBC driver used.

Example:

   | odbc_dsn = Driver={Oracle ODBC Driver};Dbq=myDBName;Uid=myUsername;Pwd=myPassword

11.1.11. sql_query_pre
----------------------

Pre-fetch query, or pre-query. Multi-value, optional, default is empty list
of queries. Applies to SQL source types (mysql, pgsql, mssql) only.

Multi-value means that you can specify several pre-queries. They are
executed before the main fetch query, and they will be exectued exactly in
order of appeareance in the configuration file. Pre-query results are
ignored.

Pre-queries are useful in a lot of ways. They are used to setup encoding,
mark records that are going to be indexed, update internal counters, set
various per-connection SQL server options and variables, and so on.

Perhaps the most frequent pre-query usage is to specify the encoding that
the server will use for the rows it returnes. It must match the encoding
that Sphinx expects (as specified by charset_type and charset_table
options). Two MySQL specific examples of setting the encoding are:

   | sql_query_pre = SET CHARACTER_SET_RESULTS=cp1251
   | sql_query_pre = SET NAMES utf8

Also specific to MySQL sources, it is useful to disable query cache (for
indexer connection only) in pre-query, because indexing queries are not
going to be re-run frequently anyway, and there's no sense in caching their
results. That could be achieved with:

   | sql_query_pre = SET SESSION query_cache_type=OFF

Example:

   | sql_query_pre = SET NAMES utf8
   | sql_query_pre = SET SESSION query_cache_type=OFF

11.1.12. sql_query
------------------

Main document fetch query. Mandatory, no default value. Applies to SQL
source types (mysql, pgsql, mssql) only.

There can be only one main query. This is the query which is used to
retrieve documents from SQL server. You can specify up to 32 full-text
fields (formally, upto SPH_MAX_FIELDS from sphinx.h), and an arbitrary
amount of attributes. All of the columns that are neither document ID (the
first one) nor attributes will be full-text indexed.

Document ID MUST be the very first field, and it MUST BE UNIQUE UNSIGNED
POSITIVE (NON-ZERO, NON-NEGATIVE) INTEGER NUMBER. It can be either 32-bit
or 64-bit, depending on how you built Sphinx; by default it builds with
32-bit IDs support but --enable-id64 option to configure allows to build
with 64-bit document and word IDs support.

Example:

   | sql_query = \
   | 	SELECT id, group_id, UNIX_TIMESTAMP(date_added) AS date_added, \
   | 		title, content \
   | 	FROM documents

11.1.13. sql_joined_field
-------------------------

Joined/payload field fetch query. Multi-value, optional, default is empty
list of queries. Applies to SQL source types (mysql, pgsql, mssql) only.

sql_joined_field lets you use two different features: joined fields, and
payloads (payload fields). It's syntax is as follows:

   | sql_joined_field = FIELD-NAME 'from'  ( 'query' | 'payload-query' \
   | 	| 'ranged-query' ); QUERY [ ; RANGE-QUERY ]

where

   * FIELD-NAME is a joined/payload field name;
   * QUERY is an SQL query that must fetch values to index.
   * RANGE-QUERY is an optional SQL query that fetches a range of values to
     index. (Added in version 2.0.1-beta.)

Joined fields let you avoid JOIN and/or GROUP_CONCAT statements in the main
document fetch query (sql_query). This can be useful when SQL-side JOIN is
slow, or needs to be offloaded on Sphinx side, or simply to emulate
MySQL-specific GROUP_CONCAT funcionality in case your database server does
not support it.

The query must return exactly 2 columns: document ID, and text to append to
a joined field. Document IDs can be duplicate, but they must be in
ascending order. All the text rows fetched for a given ID will be
concatented together, and the concatenation result will be indexed as the
entire contents of a joined field. Rows will be concatenated in the order
returned from the query, and separating whitespace will be inserted between
them. For instance, if joined field query returns the following rows:

   | ( 1, 'red' )
   | ( 1, 'right' )
   | ( 1, 'hand' )
   | ( 2, 'mysql' )
   | ( 2, 'sphinx' )

then the indexing results would be equivalent to that of adding a new text
field with a value of 'red right hand' to document 1 and 'mysql sphinx' to
document 2.

Joined fields are only indexed differently. There are no other differences
between joined fields and regular text fields.

Starting with 2.0.1-beta, ranged queries can be used when a single query is
not efficient enough or does not work because of the database driver
limitations. It works similar to the ranged queries in the main indexing
loop, see Section 3.8, <<Ranged queries>>. The range will be queried for
and fetched upfront once, then multiple queries with different $start and
$end substitutions will be run to fetch the actual data.

Payloads let you create a special field in which, instead of keyword
positions, so-called user payloads are stored. Payloads are custom integer
values attached to every keyword. They can then be used in search time to
affect the ranking.

The payload query must return exactly 3 columns: document ID; keyword; and
integer payload value. Document IDs can be duplicate, but they must be in
ascending order. Payloads must be unsigned integers within 24-bit range,
ie. from 0 to 16777215. For reference, payloads are currently internally
stored as in-field keyword positions, but that is not guaranteed and might
change in the future.

Currently, the only method to account for payloads is to use
SPH_RANK_PROXIMITY_BM25 ranker. On indexes with payload fields, it will
automatically switch to a variant that matches keywords in those fields,
computes a sum of matched payloads multiplied by field wieghts, and adds
that sum to the final rank.

Example:

   | sql_joined_field = \
   | 	tagstext from query; \
   | 	SELECT docid, CONCAT('tag',tagid) FROM tags ORDER BY docid ASC
   | 
   | sql_joined_field = bigint tag from ranged-query; \
   | 	SELECT id, tag FROM tags WHERE id>=$start AND id<=$end; \
   | 	SELECT MIN(id), MAX(id) FROM tags

11.1.14. sql_query_range
------------------------

Range query setup. Optional, default is empty. Applies to SQL source types
(mysql, pgsql, mssql) only.

Setting this option enables ranged document fetch queries (see Section 3.8,
<<Ranged queries>>). Ranged queries are useful to avoid notorious MyISAM
table locks when indexing lots of data. (They also help with other less
notorious issues, such as reduced performance caused by big result sets, or
additional resources consumed by InnoDB to serialize big read
transactions.)

The query specified in this option must fetch min and max document IDs that
will be used as range boundaries. It must return exactly two integer
fields, min ID first and max ID second; the field names are ignored.

When ranged queries are enabled, sql_query will be required to contain
$start and $end macros (because it obviously would be a mistake to index
the whole table many times over). Note that the intervals specified by
$start..$end will not overlap, so you should not remove document IDs that
are exactly equal to $start or $end from your query. The example in
Section 3.8, <<Ranged queries>>) illustrates that; note how it uses
greater-or-equal and less-or-equal comparisons.

Example:

   | sql_query_range = SELECT MIN(id),MAX(id) FROM documents

11.1.15. sql_range_step
-----------------------

Range query step. Optional, default is 1024. Applies to SQL source types
(mysql, pgsql, mssql) only.

Only used when ranged queries are enabled. The full document IDs interval
fetched by sql_query_range will be walked in this big steps. For example,
if min and max IDs fetched are 12 and 3456 respectively, and the step is
1000, indexer will call sql_query several times with the following
substitutions:

   * $start=12, $end=1011
   * $start=1012, $end=2011
   * $start=2012, $end=3011
   * $start=3012, $end=3456

Example:

   | sql_range_step = 1000

11.1.16. sql_query_killlist
---------------------------

Kill-list query. Optional, default is empty (no query). Applies to SQL
source types (mysql, pgsql, mssql) only. Introduced in version 0.9.9-rc1.

This query is expected to return a number of 1-column rows, each containing
just the document ID. The returned document IDs are stored within an index.
Kill-list for a given index suppresses results from other indexes,
depending on index order in the query. The intended use is to help
implement deletions and updates on existing indexes without rebuilding
(actually even touching them), and especially to fight phantom results
problem.

Let us dissect an example. Assume we have two indexes, 'main' and 'delta'.
Assume that documents 2, 3, and 5 were deleted since last reindex of
'main', and documents 7 and 11 were updated (ie. their text contents were
changed). Assume that a keyword 'test' occurred in all these mentioned
documents when we were indexing 'main'; still occurs in document 7 as we
index 'delta'; but does not occur in document 11 any more. We now reindex
delta and then search through both these indexes in proper (least to most
recent) order:

   | $res = $cl->Query ( "test", "main delta" );

First, we need to properly handle deletions. The result set should not
contain documents 2, 3, or 5. Second, we also need to avoid phantom
results. Unless we do something about it, document 11 will appear in search
results! It will be found in 'main' (but not 'delta'). And it will make it
to the final result set unless something stops it.

Kill-list, or K-list for short, is that something. Kill-list attached to
'delta' will suppress the specified rows from all the preceding indexes, in
this case just 'main'. So to get the expected results, we should put all
the updated and deleted document IDs into it.

Example:

   | sql_query_killlist = \
   | 	SELECT id FROM documents WHERE updated_ts>=@last_reindex UNION \
   | 	SELECT id FROM documents_deleted WHERE deleted_ts>=@last_reindex

11.1.17. sql_attr_uint
----------------------

Unsigned integer attribute declaration. Multi-value (there might be
multiple attributes declared), optional. Applies to SQL source types
(mysql, pgsql, mssql) only.

The column value should fit into 32-bit unsigned integer range. Values
outside this range will be accepted but wrapped around. For instance, -1
will be wrapped around to 2^32-1 or 4,294,967,295.

You can specify bit count for integer attributes by appending ':BITCOUNT'
to attribute name (see example below). Attributes with less than default
32-bit size, or bitfields, perform slower. But they require less RAM when
using extern storage: such bitfields are packed together in 32-bit chunks
in .spa attribute data file. Bit size settings are ignored if using inline
storage.

Example:

   | sql_attr_uint = group_id
   | sql_attr_uint = forum_id:9 # 9 bits for forum_id

11.1.18. sql_attr_bool
----------------------

Boolean attribute declaration. Multi-value (there might be multiple
attributes declared), optional. Applies to SQL source types (mysql, pgsql,
mssql) only. Equivalent to sql_attr_uint declaration with a bit count of 1.

Example:

   | sql_attr_bool = is_deleted # will be packed to 1 bit

11.1.19. sql_attr_bigint
------------------------

64-bit signed integer attribute declaration. Multi-value (there might be
multiple attributes declared), optional. Applies to SQL source types
(mysql, pgsql, mssql) only. Note that unlike sql_attr_uint, these values
are signed. Introduced in version 0.9.9-rc1.

Example:

   | sql_attr_bigint = my_bigint_id

11.1.20. sql_attr_timestamp
---------------------------

UNIX timestamp attribute declaration. Multi-value (there might be multiple
attributes declared), optional. Applies to SQL source types (mysql, pgsql,
mssql) only.

Timestamps can store date and time in the range of Jan 01, 1970 to Jan 19,
2038 with a precision of one second. The expected column value should be
a timestamp in UNIX format, ie. 32-bit unsigned integer number of seconds
elapsed since midnight, January 01, 1970, GMT. Timestamps are internally
stored and handled as integers everywhere. But in addition to working with
timestamps as integers, it's also legal to use them along with different
date-based functions, such as time segments sorting mode, or
day/week/month/year extraction for GROUP BY.

Note that DATE or DATETIME column types in MySQL can not be directly used
as timestamp attributes in Sphinx; you need to explicitly convert such
columns using UNIX_TIMESTAMP function (if data is in range).

Note timestamps can not represent dates before January 01, 1970, and
UNIX_TIMESTAMP() in MySQL will not return anything expected. If you only
needs to work with dates, not times, consider TO_DAYS() function in MySQL
instead.

Example:

   | # sql_query = ... UNIX_TIMESTAMP(added_datetime) AS added_ts ...
   | sql_attr_timestamp = added_ts

11.1.21. sql_attr_str2ordinal
-----------------------------

Ordinal string number attribute declaration. Multi-value (there might be
multiple attributes declared), optional. Applies to SQL source types
(mysql, pgsql, mssql) only.

This attribute type (so-called ordinal, for brevity) is intended to allow
sorting by string values, but without storing the strings themselves. When
indexing ordinals, string values are fetched from database, temporarily
stored, sorted, and then replaced by their respective ordinal numbers in
the array of sorted strings. So, the ordinal number is an integer such that
sorting by it produces the same result as if lexicographically sorting by
original strings. by string values lexicographically.

Earlier versions could consume a lot of RAM for indexing ordinals. Starting
with revision r1112, ordinals accumulation and sorting also runs in fixed
memory (at the cost of using additional temporary disk space), and honors
mem_limit settings.

Ideally the strings should be sorted differently, depending on the encoding
and locale. For instance, if the strings are known to be Russian text in
KOI8R encoding, sorting the bytes 0xE0, 0xE1, and 0xE2 should produce 0xE1,
0xE2 and 0xE0, because in KOI8R value 0xE0 encodes a character that is
(noticeably) after characters encoded by 0xE1 and 0xE2. Unfortunately,
Sphinx does not support that at the moment and will simply sort the strings
bytewise.

Note that the ordinals are by construction local to each index, and it's
therefore impossible to merge ordinals while retaining the proper order.
The processed strings are replaced by their sequential number in the index
they occurred in, but different indexes have different sets of strings. For
instance, if 'main' index contains strings "aaa", "bbb", "ccc", and so on
up to "zzz", they'll be assigned numbers 1, 2, 3, and so on up to 26,
respectively. But then if 'delta' only contains "zzz" the assigned number
will be 1. And after the merge, the order will be broken. Unfortunately,
this is impossible to workaround without storing the original strings (and
once Sphinx supports storing the original strings, ordinals will not be
necessary any more).

Example:

   | sql_attr_str2ordinal = author_name

11.1.22. sql_attr_float
-----------------------

Floating point attribute declaration. Multi-value (there might be multiple
attributes declared), optional. Applies to SQL source types (mysql, pgsql,
mssql) only.

The values will be stored in single precision, 32-bit IEEE 754 format.
Represented range is approximately from 1e-38 to 1e+38. The amount of
decimal digits that can be stored precisely is approximately 7. One
important usage of the float attributes is storing latitude and longitude
values (in radians), for further usage in query-time geosphere distance
calculations.

Example:

   | sql_attr_float = lat_radians
   | sql_attr_float = long_radians

11.1.23. sql_attr_multi
-----------------------

Multi-valued attribute (MVA) declaration. Multi-value (ie. there may be
more than one such attribute declared), optional. Applies to SQL source
types (mysql, pgsql, mssql) only.

Plain attributes only allow to attach 1 value per each document. However,
there are cases (such as tags or categories) when it is desired to attach
multiple values of the same attribute and be able to apply filtering or
grouping to value lists.

The declaration format is as follows (backslashes are for clarity only;
everything can be declared in a single line as well):

   | sql_attr_multi = ATTR-TYPE ATTR-NAME 'from' SOURCE-TYPE \
   | 	[;QUERY] \
   | 	[;RANGE-QUERY]

where

   * ATTR-TYPE is 'uint', 'bigint' or 'timestamp'
   * SOURCE-TYPE is 'field', 'query', or 'ranged-query'
   * QUERY is SQL query used to fetch all ( docid, attrvalue ) pairs
   * RANGE-QUERY is SQL query used to fetch min and max ID values, similar
     to 'sql_query_range'

Example:

   | sql_attr_multi = uint tag from query; SELECT id, tag FROM tags
   | sql_attr_multi = bigint tag from ranged-query; \
   | 	SELECT id, tag FROM tags WHERE id>=$start AND id<=$end; \
   | 	SELECT MIN(id), MAX(id) FROM tags

11.1.24. sql_attr_string
------------------------

String attribute declaration. Multi-value (ie. there may be more than one
such attribute declared), optional. Applies to SQL source types (mysql,
pgsql, mssql) only. Introduced in version 1.10-beta.

String attributes can store arbitrary strings attached to every document.
There's a fixed size limit of 4 MB per value. Also, searchd will currently
cache all the values in RAM, which is an additional implicit limit.

Starting from 2.0.1-beta string attributes can be used for sorting and
grouping(ORDER BY, GROUP BY, WITHING GROUP ORDER BY). Note that attributes
declared using sql_attr_string will not be full-text indexed; you can use
sql_field_string directive for that.

Example:

   | sql_attr_string = title # will be stored but will not be indexed

11.1.25. sql_attr_str2wordcount
-------------------------------

Word-count attribute declaration. Multi-value (ie. there may be more than
one such attribute declared), optional. Applies to SQL source types (mysql,
pgsql, mssql) only. Introduced in version 1.10-beta.

Word-count attribute takes a string column, tokenizes it according to index
settings, and stores the resulting number of tokens in an attribute. This
number of tokens ("word count") is a normal integer that can be later used,
for instance, in custom ranking expressions (boost shorter titles, help
identify exact field matches, etc).

Example:

   | sql_attr_str2wordcount = title_wc

11.1.26. sql_column_buffers
---------------------------

Per-column buffer sizes. Optional, default is empty (deduce the sizes
automatically). Applies to odbc, mssql source types only. Introduced in
version 2.0.1-beta.

ODBC and MS SQL drivers sometimes can not return the maximum actual column
size to be expected. For instance, NVARCHAR(MAX) columns always report
their length as 2147483647 bytes to indexer even though the actually used
length is likely considerably less. However, the receiving buffers still
need to be allocated upfront, and their sizes have to be determined. When
the driver does not report the column length at all, Sphinx allocates
default 1 KB buffers for each non-char column, and 1 MB buffers for each
char column. Driver-reported column length also gets clamped by an upper
limie of 8 MB, so in case the driver reports (almost) a 2 GB column length,
it will be clamped and a 8 MB buffer will be allocated instead for that
column. These hard-coded limits can be overridden using the
sql_column_buffers directive, either in order to save memory on actually
shorter columns, or overcome the 8 MB limit on actually longer columns. The
directive values must be a comma-separated lists of selected column names
and sizes:

   | sql_column_buffers = <colname>=<size>[K|M] [, ...]

Example:

   | sql_query = SELECT id, mytitle, mycontent FROM documents
   | sql_column_buffers = mytitle=64K, mycontent=10M

11.1.27. sql_field_string
-------------------------

Combined string attribute and full-text field declaration. Multi-value (ie.
there may be more than one such attribute declared), optional. Applies to
SQL source types (mysql, pgsql, mssql) only. Introduced in version
1.10-beta.

sql_attr_string only stores the column value but does not full-text index
it. In some cases it might be desired to both full-text index the column
and store it as attribute. sql_field_string lets you do exactly that. Both
the field and the attribute will be named the same.

Example:

   | sql_field_string = title # will be both indexed and stored

11.1.28. sql_field_str2wordcount
--------------------------------

Combined word-count attribute and full-text field declaration. Multi-value
(ie. there may be more than one such attribute declared), optional. Applies
to SQL source types (mysql, pgsql, mssql) only. Introduced in version
1.10-beta.

sql_attr_str2wordcount only stores the column word count but does not
full-text index it. In some cases it might be desired to both full-text
index the column and also have the count. sql_field_str2wordcount lets you
do exactly that. Both the field and the attribute will be named the same.

Example:

   | sql_field_str2wordcount = title # will be indexed, and counted/stored

11.1.29. sql_file_field
-----------------------

File based field declaration. Applies to SQL source types (mysql, pgsql,
mssql) only. Introduced in version 1.10-beta.

This directive makes indexer interpret field contents as a file name, and
load and index the referred file. Files larger than max_file_field_buffer
in size are skipped. Any errors during the file loading (IO errors, missed
limits, etc) will be reported as indexing warnings and will not early
terminate the indexing. No content will be indexed for such files.

Example:

   | sql_file_field = my_file_path # load and index files referred to by my_file_path

11.1.30. sql_query_post
-----------------------

Post-fetch query. Optional, default value is empty. Applies to SQL source
types (mysql, pgsql, mssql) only.

This query is executed immediately after sql_query completes successfully.
When post-fetch query produces errors, they are reported as warnings, but
indexing is not terminated. It's result set is ignored. Note that indexing
is not yet completed at the point when this query gets executed, and
further indexing still may fail. Therefore, any permanent updates should
not be done from here. For instance, updates on helper table that
permanently change the last successfully indexed ID should not be run from
post-fetch query; they should be run from post-index query instead.

Example:

   | sql_query_post = DROP TABLE my_tmp_table

11.1.31. sql_query_post_index
-----------------------------

Post-index query. Optional, default value is empty. Applies to SQL source
types (mysql, pgsql, mssql) only.

This query is executed when indexing is fully and succesfully completed. If
this query produces errors, they are reported as warnings, but indexing is
not terminated. It's result set is ignored. $maxid macro can be used in its
text; it will be expanded to maximum document ID which was actually fetched
from the database during indexing. If no documents were indexed, $maxid
will be expanded to 0.

Example:

   | sql_query_post_index = REPLACE INTO counters ( id, val ) \
   |     VALUES ( 'max_indexed_id', $maxid )

11.1.32. sql_ranged_throttle
----------------------------

Ranged query throttling period, in milliseconds. Optional, default is 0 (no
throttling). Applies to SQL source types (mysql, pgsql, mssql) only.

Throttling can be useful when indexer imposes too much load on the database
server. It causes the indexer to sleep for given amount of milliseconds
once per each ranged query step. This sleep is unconditional, and is
performed before the fetch query.

Example:

   | sql_ranged_throttle = 1000 # sleep for 1 sec before each query step

11.1.33. sql_query_info
-----------------------

Document info query. Optional, default is empty. Applies to mysql source
type only.

Only used by CLI search to fetch and display document information, only
works with MySQL at the moment, and only intended for debugging purposes.
This query fetches the row that will be displayed by CLI search utility for
each document ID. It is required to contain $id macro that expands to the
queried document ID.

Example:

   | sql_query_info = SELECT * FROM documents WHERE id=$id

11.1.34. xmlpipe_command
------------------------

Shell command that invokes xmlpipe stream producer. Mandatory. Applies to
xmlpipe and xmlpipe2 source types only.

Specifies a command that will be executed and which output will be parsed
for documents. Refer to Section 3.9, <<xmlpipe data source>> or
Section 3.10, <<xmlpipe2 data source>> for specific format description.

Example:

   | xmlpipe_command = cat /home/sphinx/test.xml

11.1.35. xmlpipe_field
----------------------

xmlpipe field declaration. Multi-value, optional. Applies to xmlpipe2
source type only. Refer to Section 3.10, <<xmlpipe2 data source>>.

Example:

   | xmlpipe_field = subject
   | xmlpipe_field = content

11.1.36. xmlpipe_field_string
-----------------------------

xmlpipe field and string attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Refer to Section 3.10, <<xmlpipe2
data source>>. Introduced in version 1.10-beta.

Makes the specified XML element indexed as both a full-text field and
a string attribute. Equivalent to <sphinx:field name="field"
attr="string"/> declaration within the XML file.

Example:

   | xmlpipe_field_string = subject

11.1.37. xmlpipe_field_wordcount
--------------------------------

xmlpipe field and word count attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Refer to Section 3.10, <<xmlpipe2
data source>>. Introduced in version 1.10-beta.

Makes the specified XML element indexed as both a full-text field and
a word count attribute. Equivalent to <sphinx:field name="field"
attr="wordcount"/> declaration within the XML file.

Example:

   | xmlpipe_field_wordcount = subject

11.1.38. xmlpipe_attr_uint
--------------------------

xmlpipe integer attribute declaration. Multi-value, optional. Applies to
xmlpipe2 source type only. Syntax fully matches that of sql_attr_uint.

Example:

   | xmlpipe_attr_uint = author_id

11.1.39. xmlpipe_attr_bigint
----------------------------

xmlpipe signed 64-bit integer attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Syntax fully matches that of
sql_attr_bigint.

Example:

   | xmlpipe_attr_bigint = my_bigint_id

11.1.40. xmlpipe_attr_bool
--------------------------

xmlpipe boolean attribute declaration. Multi-value, optional. Applies to
xmlpipe2 source type only. Syntax fully matches that of sql_attr_bool.

Example:

   | xmlpipe_attr_bool = is_deleted # will be packed to 1 bit

11.1.41. xmlpipe_attr_timestamp
-------------------------------

xmlpipe UNIX timestamp attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Syntax fully matches that of
sql_attr_timestamp.

Example:

   | xmlpipe_attr_timestamp = published

11.1.42. xmlpipe_attr_str2ordinal
---------------------------------

xmlpipe string ordinal attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Syntax fully matches that of
sql_attr_str2ordinal.

Example:

   | xmlpipe_attr_str2ordinal = author_sort

11.1.43. xmlpipe_attr_float
---------------------------

xmlpipe floating point attribute declaration. Multi-value, optional.
Applies to xmlpipe2 source type only. Syntax fully matches that of
sql_attr_float.

Example:

   | xmlpipe_attr_float = lat_radians
   | xmlpipe_attr_float = long_radians

11.1.44. xmlpipe_attr_multi
---------------------------

xmlpipe MVA attribute declaration. Multi-value, optional. Applies to
xmlpipe2 source type only.

This setting declares an MVA attribute tag in xmlpipe2 stream. The contents
of the specified tag will be parsed and a list of integers that will
constitute the MVA will be extracted, similar to how sql_attr_multi parses
SQL column contents when 'field' MVA source type is specified.

Example:

   | xmlpipe_attr_multi = taglist

11.1.45. xmlpipe_attr_multi_64
------------------------------

xmlpipe MVA attribute declaration. Declares the BIGINT (signed 64-bit
integer) MVA attribute. Multi-value, optional. Applies to xmlpipe2 source
type only.

This setting declares an MVA attribute tag in xmlpipe2 stream. The contents
of the specified tag will be parsed and a list of integers that will
constitute the MVA will be extracted, similar to how sql_attr_multi parses
SQL column contents when 'field' MVA source type is specified.

Example:

   | xmlpipe_attr_multi_64 = taglist

11.1.46. xmlpipe_attr_string
----------------------------

xmlpipe string declaration. Multi-value, optional. Applies to xmlpipe2
source type only. Introduced in version 1.10-beta.

This setting declares a string attribute tag in xmlpipe2 stream. The
contents of the specified tag will be parsed and stored as a string value.

Example:

   | xmlpipe_attr_string = subject

11.1.47. xmlpipe_fixup_utf8
---------------------------

Perform Sphinx-side UTF-8 validation and filtering to prevent XML parser
from choking on non-UTF-8 documents. Optional, default is 0. Applies to
xmlpipe2 source type only.

Under certain occasions it might be hard or even impossible to guarantee
that the incoming XMLpipe2 document bodies are in perfectly valid and
conforming UTF-8 encoding. For instance, documents with national
single-byte encodings could sneak into the stream. libexpat XML parser is
fragile, meaning that it will stop processing in such cases. UTF8 fixup
feature lets you avoid that. When fixup is enabled, Sphinx will preprocess
the incoming stream before passing it to the XML parser and replace invalid
UTF-8 sequences with spaces.

Example:

   | xmlpipe_fixup_utf8 = 1

11.1.48. mssql_winauth
----------------------

MS SQL Windows authentication flag. Boolean, optional, default value is
0 (false). Applies to mssql source type only. Introduced in version
0.9.9-rc1.

Whether to use currently logged in Windows account credentials for
authentication when connecting to MS SQL Server. Note that when running
searchd as a service, account user can differ from the account you used to
install the service.

Example:

   | mssql_winauth = 1

11.1.49. mssql_unicode
----------------------

MS SQL encoding type flag. Boolean, optional, default value is 0 (false).
Applies to mssql source type only. Introduced in version 0.9.9-rc1.

Whether to ask for Unicode or single-byte data when querying MS SQL Server.
This flag must be in sync with charset_type directive; that is, to index
Unicode data, you must set both charset_type in the index (to 'utf-8') and
mssql_unicode in the source (to 1). For reference, MS SQL will actually
return data in UCS-2 encoding instead of UTF-8, but Sphinx will
automatically handle that.

Example:

   | mssql_unicode = 1

11.1.50. unpack_zlib
--------------------

Columns to unpack using zlib (aka deflate, aka gunzip). Multi-value,
optional, default value is empty list of columns. Applies to SQL source
types (mysql, pgsql, mssql) only. Introduced in version 0.9.9-rc1.

Columns specified using this directive will be unpacked by indexer using
standard zlib algorithm (called deflate and also implemented by gunzip).
When indexing on a different box than the database, this lets you offload
the database, and save on network traffic. The feature is only available if
zlib and zlib-devel were both available during build time.

Example:

   | unpack_zlib = col1
   | unpack_zlib = col2

11.1.51. unpack_mysqlcompress
-----------------------------

Columns to unpack using MySQL UNCOMPRESS() algorithm. Multi-value,
optional, default value is empty list of columns. Applies to SQL source
types (mysql, pgsql, mssql) only. Introduced in version 0.9.9-rc1.

Columns specified using this directive will be unpacked by indexer using
modified zlib algorithm used by MySQL COMPRESS() and UNCOMPRESS()
functions. When indexing on a different box than the database, this lets
you offload the database, and save on network traffic. The feature is only
available if zlib and zlib-devel were both available during build time.

Example:

   | unpack_mysqlcompress = body_compressed
   | unpack_mysqlcompress = description_compressed

11.1.52. unpack_mysqlcompress_maxsize
-------------------------------------

Buffer size for UNCOMPRESS()ed data. Optional, default value is 16M.
Introduced in version 0.9.9-rc1.

When using unpack_mysqlcompress, due to implementation intrincacies it is
not possible to deduce the required buffer size from the compressed data.
So the buffer must be preallocated in advance, and unpacked data can not go
over the buffer size. This option lets you control the buffer size, both to
limit indexer memory use, and to enable unpacking of really long data
fields if necessary.

Example:

   | unpack_mysqlcompress_maxsize = 1M

11.2. Index configuration options
=================================

11.2.1. type
------------

Index type. Known values are 'plain', 'distributed', and 'rt'. Optional,
default is 'plain' (plain local index).

Sphinx supports several different types of indexes. Versions 0.9.x
supported two index types: plain local indexes that are stored and
processed on the local machine; and distributed indexes, that involve not
only local searching but querying remote searchd instances over the network
as well (see Section 5.8, <<Distributed searching>>). Version 1.10-beta
also adds support for so-called real-time indexes (or RT indexes for short)
that are also stored and processed locally, but additionally allow for
on-the-fly updates of the full-text index (see Chapter 4, Real-time
indexes). Note that attributes can be updated on-the-fly using either plain
local indexes or RT ones.

Index type setting lets you choose the needed type. By default, plain local
index type will be assumed.

Example:

   | type = distributed

11.2.2. source
--------------

Adds document source to local index. Multi-value, mandatory.

Specifies document source to get documents from when the current index is
indexed. There must be at least one source. There may be multiple sources,
without any restrictions on the source types: ie. you can pull part of the
data from MySQL server, part from PostgreSQL, part from the filesystem
using xmlpipe2 wrapper.

However, there are some restrictions on the source data. First, document
IDs must be globally unique across all sources. If that condition is not
met, you might get unexpected search results. Second, source schemas must
be the same in order to be stored within the same index.

No source ID is stored automatically. Therefore, in order to be able to
tell what source the matched document came from, you will need to store
some additional information yourself. Two typical approaches include:

   1. mangling document ID and encoding source ID in it:

      | source src1
      | {
      | 	sql_query = SELECT id*10+1, ... FROM table1
      | 	...
      | }
      | 
      | source src2
      | {
      | 	sql_query = SELECT id*10+2, ... FROM table2
      | 	...
      | }

   2. storing source ID simply as an attribute:

      | source src1
      | {
      | 	sql_query = SELECT id, 1 AS source_id FROM table1
      | 	sql_attr_uint = source_id
      | 	...
      | }
      | 
      | source src2
      | {
      | 	sql_query = SELECT id, 2 AS source_id FROM table2
      | 	sql_attr_uint = source_id
      | 	...
      | }

Example:

   | source = srcpart1
   | source = srcpart2
   | source = srcpart3

11.2.3. path
------------

Index files path and file name (without extension). Mandatory.

Path specifies both directory and file name, but without extension. indexer
will append different extensions to this path when generating final names
for both permanent and temporary index files. Permanent data files have
several different extensions starting with '.sp'; temporary files'
extensions start with '.tmp'. It's safe to remove .tmp* files is if indexer
fails to remove them automatically.

For reference, different index files store the following data:

   * .spa stores document attributes (used in extern docinfo storage mode
     only);
   * .spd stores matching document ID lists for each word ID;
   * .sph stores index header information;
   * .spi stores word lists (word IDs and pointers to .spd file);
   * .spk stores kill-lists;
   * .spm stores MVA data;
   * .spp stores hit (aka posting, aka word occurence) lists for each word
     ID;
   * .sps stores string attribute data.

Example:

   | path = /var/data/test1

11.2.4. docinfo
---------------

Document attribute values (docinfo) storage mode. Optional, default is
'extern'. Known values are 'none', 'extern' and 'inline'.

Docinfo storage mode defines how exactly docinfo will be physically stored
on disk and RAM. "none" means that there will be no docinfo at all (ie. no
attributes). Normally you need not to set "none" explicitly because Sphinx
will automatically select "none" when there are no attributes configured.
"inline" means that the docinfo will be stored in the .spd file, along with
the document ID lists. "extern" means that the docinfo will be stored
separately (externally) from document ID lists, in a special .spa file.

Basically, externally stored docinfo must be kept in RAM when querying. for
performance reasons. So in some cases "inline" might be the only option.
However, such cases are infrequent, and docinfo defaults to "extern". Refer
to Section 3.3, <<Attributes>> for in-depth discussion and RAM usage
estimates.

Example:

   | docinfo = inline

11.2.5. mlock
-------------

Memory locking for cached data. Optional, default is 0 (do not call
mlock()).

For search performance, searchd preloads a copy of .spa and .spi files in
RAM, and keeps that copy in RAM at all times. But if there are no searches
on the index for some time, there are no accesses to that cached copy, and
OS might decide to swap it out to disk. First queries to such "cooled down"
index will cause swap-in and their latency will suffer.

Setting mlock option to 1 makes Sphinx lock physical RAM used for that
cached data using mlock(2) system call, and that prevents swapping (see man
2 mlock for details). mlock(2) is a privileged call, so it will require
searchd to be either run from root account, or be granted enough privileges
otherwise. If mlock() fails, a warning is emitted, but index continues
working.

Example:

   | mlock = 1

11.2.6. morphology
------------------

A list of morphology preprocessors to apply. Optional, default is empty (do
not apply any preprocessor).

Morphology preprocessors can be applied to the words being indexed to
replace different forms of the same word with the base, normalized form.
For instance, English stemmer will normalize both "dogs" and "dog" to
"dog", making search results for both searches the same.

Built-in preprocessors include English stemmer, Russian stemmer (that
supports UTF-8 and Windows-1251 encodings), Soundex, and Metaphone. The
latter two replace the words with special phonetic codes that are equal is
words are phonetically close. Additional stemmers provided by Snowball
project libstemmer library can be enabled at compile time using
--with-libstemmer configure option. Built-in English and Russian stemmers
should be faster than their libstemmer counterparts, but can produce
slightly different results, because they are based on an older version.
Metaphone implementation is based on Double Metaphone algorithm and indexes
the primary code.

Built-in values that are available for use in morphology option are as
follows:

   * none - do not perform any morphology processing;
   * stem_en - apply Porter's English stemmer;
   * stem_ru - apply Porter's Russian stemmer;
   * stem_enru - apply Porter's English and Russian stemmers;
   * stem_cz - apply Czech stemmer;
   * soundex - replace keywords with their SOUNDEX code;
   * metaphone - replace keywords with their METAPHONE code.

Additional values provided by libstemmer are in 'libstemmer_XXX' format,
where XXX is libstemmer algorithm codename (refer to
libstemmer_c/libstemmer/modules.txt for a complete list).

Several stemmers can be specified (comma-separated). They will be applied
to incoming words in the order they are listed, and the processing will
stop once one of the stemmers actually modifies the word. Also when
wordforms feature is enabled the word will be looked up in word forms
dictionary first, and if there is a matching entry in the dictionary,
stemmers will not be applied at all. Or in other words, wordforms can be
used to implement stemming exceptions.

Example:

   | morphology = stem_en, libstemmer_sv

11.2.7. dict
------------

The keywords dictionary type. Known values are 'crc' and 'keywords'.
Optional, default is 'crc'. Introduced in version 2.0.1-beta.

CRC dictionary mode (dict=crc) is the default dictionary type in Sphinx,
and the only one available until version 2.0.1-beta. Keywords dictionary
mode (dict=keywords) was added in 2.0.1-beta, primarly to (greatly) reduce
indexing impact and enable substring searches on huge collections. They
also eliminate the chance of CRC32 collisions. In 2.0.1-beta, that mode was
only supported for disk indexes. Starting with 2.0.2-beta, RT indexes are
also supported.

CRC dictionaries never store the original keyword text in the index.
Instead, keywords are replaced with their control sum value (either CRC32
or FNV64, depending whether Sphinx was built with --enable-id64) both when
searching and indexing, and that value is used internally in the index.

That approach has two drawbacks. First, in CRC32 case there is a chance of
control sum collision between several pairs of different keywords, growing
quadratically with the number of unique keywords in the index. (FNV64 case
is unaffected in practice, as a chance of a single FNV64 collision in
a dictionary of 1 billion entries is approximately 1:16, or 6.25 percent.
And most dictionaries will be much more compact that a billion keywords, as
a typical spoken human language has in the region of 1 to 10 million word
forms.) Second, and more importantly, substring searches are not directly
possible with control sums. Sphinx alleviated that by pre-indexing all the
possible substrings as separate keywords (see Section 11.2.18,
<<min_prefix_len>>, Section 11.2.19, <<min_infix_len>> directives). That
actually has an added benefit of matching substrings in the quickest way
possible. But at the same time pre-indexing all substrings grows the index
size a lot (factors of 3-10x and even more would not be unusual) and
impacts the indexing time respectively, rendering substring searches on big
indexes rather impractical.

Keywords dictionary, introduced in 2.0.1-beta, fixes both these drawbacks.
It stores the keywords in the index and performs search-time wildcard
expansion. For example, a search for a 'test*' prefix could internally
expand to 'test|tests|testing' query based on the dictionary contents. That
expansion is fully transparent to the application, except that the separate
per-keyword statistics for all the actually matched keywords would now also
be reported.

Indexing with keywords dictionary should be 1.1x to 1.3x slower compared to
regular, non-substring indexing - but times faster compared to substring
indexing (either prefix or infix). Index size should only be slightly
bigger that than of the regular non-substring index, with a 1..10% percent
total difference Regular keyword searching time must be very close or
identical across all three discussed index kinds (CRC non-substring, CRC
substring, keywords). Substring searching time can vary greatly depending
on how many actual keywords match the given substring (in other words, into
how many keywords does the search term expand). The maximum number of
keywords matched is restricted by the expansion_limit directive.

Essentially, keywords and CRC dictionaries represent the two different
trade-off substring searching decisions. You can choose to either sacrifice
indexing time and index size in favor of top-speed worst-case searches (CRC
dictionary), or only slightly impact indexing time but sacrifice worst-case
searching time when the prefix expands into very many keywords (keywords
dictionary).

Example:

   | dict = keywords

11.2.8. index_sp
----------------

Whether to detect and index sentence and paragraph boundaries. Optional,
default is 0 (do not detect and index). Introduced in version 2.0.1-beta.

This directive enables sentence and paragraph boundary indexing. It's
required for the SENTENCE and PARAGRAPH operators to work. Sentence
boundary detection is based on plain text analysis, so you only need to set
index_sp = 1 to enable it. Paragraph detection is however based on HTML
markup, and happens in the HTML stripper. So to index paragraph locations
you also need to enable the stripper by specifying html_strip = 1. Both
types of boundaries are detected based on a few built-in rules enumerated
just below.

Sentence boundary detection rules are as follows.

   * Question and excalamation signs (? and !) are always a sentence
     boundary.
   * Trailing dot (.) is a sentence boundary, except:

      * When followed by a letter. That's considered a part of an
        abbreviation (as in "S.T.A.L.K.E.R" or "Goldman Sachs S.p.A.").
      * When followed by a comma. That's considered an abbreviation
        followed by a comma (as in "Telecom Italia S.p.A., founded in
        1994").
      * When followed by a space and a small letter. That's considered an
        abbreviation within a sentence (as in "News Corp. announced in
        Februrary").
      * When preceded by a space and a capital letter, and followed by
        a space. That's considered a middle initial (as in "John D. Doe").

Paragraph boundaries are inserted at every block-level HTML tag. Namely,
those are (as taken from HTML 4 standard) ADDRESS, BLOCKQUOTE, CAPTION,
CENTER, DD, DIV, DL, DT, H1, H2, H3, H4, H5, LI, MENU, OL, P, PRE, TABLE,
TBODY, TD, TFOOT, TH, THEAD, TR, and UL.

Both sentences and paragraphs increment the keyword position counter by 1.

Example:

   | index_sp = 1

11.2.9. index_zones
-------------------

A list of in-field HTML/XML zones to index. Optional, default is empty (do
not index zones). Introduced in version 2.0.1-beta.

Zones can be formally defined as follows. Everything between an opening and
a matching closing tag is called a span, and the aggregate of all spans
corresponding sharing the same tag name is called a zone. For instance,
everything between the occurrences of <H1> and </H1> in the document field
belongs to H1 zone.

Zone indexing, enabled by index_zones directive, is an optional extension
of the HTML stripper. So it will also require that the stripper is enabled
(with html_strip = 1). The value of the index_zones should be
a comma-separated list of those tag names and wildcards (ending with
a star) that should be indexed as zones.

Zones can nest and overlap arbitrarily. The only requirement is that every
opening tag has a matching tag. You can also have an arbitrary number of
both zones (as in unique zone names, such as H1) and spans (all the
occurrences of those H1 tags) in a document. Once indexed, zones can then
be used for matching with the ZONE operator, see Section 5.3, <<Extended
query syntax>>.

Example:

   | index_zones = h*, th, title

11.2.10. min_stemming_len
-------------------------

Minimum word length at which to enable stemming. Optional, default is
1 (stem everything). Introduced in version 0.9.9-rc1.

Stemmers are not perfect, and might sometimes produce undesired results.
For instance, running "gps" keyword through Porter stemmer for English
results in "gp", which is not really the intent. min_stemming_len feature
lets you suppress stemming based on the source word length, ie. to avoid
stemming too short words. Keywords that are shorter than the given
threshold will not be stemmed. Note that keywords that are exactly as long
as specified will be stemmed. So in order to avoid stemming 3-character
keywords, you should specify 4 for the value. For more finely grained
control, refer to wordforms feature.

Example:

   | min_stemming_len = 4

11.2.11. stopwords
------------------

Stopword files list (space separated). Optional, default is empty.

Stopwords are the words that will not be indexed. Typically you'd put most
frequent words in the stopwords list because they do not add much value to
search results but consume a lot of resources to process.

You can specify several file names, separated by spaces. All the files will
be loaded. Stopwords file format is simple plain text. The encoding must
match index encoding specified in charset_type. File data will be tokenized
with respect to charset_table settings, so you can use the same separators
as in the indexed data. The stemmers will also be applied when parsing
stopwords file.

While stopwords are not indexed, they still do affect the keyword
positions. For instance, assume that "the" is a stopword, that document
1 contains the line "in office", and that document 2 contains "in the
office". Searching for "in office" as for exact phrase will only return the
first document, as expected, even though "the" in the second one is
stopped.

Stopwords files can either be created manually, or semi-automatically.
indexer provides a mode that creates a frequency dictionary of the index,
sorted by the keyword frequency, see --buildstops and --buildfreqs switch
in Section 6.1, <<indexer command reference>>. Top keywords from that
dictionary can usually be used as stopwords.

Example:

   | stopwords = /usr/local/sphinx/data/stopwords.txt
   | stopwords = stopwords-ru.txt stopwords-en.txt

11.2.12. wordforms
------------------

Word forms dictionary. Optional, default is empty.

Word forms are applied after tokenizing the incoming text by charset_table
rules. They essentialy let you replace one word with another. Normally,
that would be used to bring different word forms to a single normal form
(eg. to normalize all the variants such as "walks", "walked", "walking" to
the normal form "walk"). It can also be used to implement stemming
exceptions, because stemming is not applied to words found in the forms
list.

Dictionaries are used to normalize incoming words both during indexing and
searching. Therefore, to pick up changes in wordforms file it's required to
reindex and restart searchd.

Word forms support in Sphinx is designed to support big dictionaries well.
They moderately affect indexing speed: for instance, a dictionary with
1 million entries slows down indexing about 1.5 times. Searching speed is
not affected at all. Additional RAM impact is roughly equal to the
dictionary file size, and dictionaries are shared across indexes: ie. if
the very same 50 MB wordforms file is specified for 10 different indexes,
additional searchd RAM usage will be about 50 MB.

Dictionary file should be in a simple plain text format. Each line should
contain source and destination word forms, in exactly the same encoding as
specified in charset_type, separated by "greater" sign. Rules from the
charset_table will be applied when the file is loaded. So basically it's as
case sensitive as your other full-text indexed data, ie. typically case
insensitive. Here's the file contents sample:

   | walks > walk
   | walked > walk
   | walking > walk

There is a bundled spelldump utility that helps you create a dictionary
file in the format Sphinx can read from source .dict and .aff dictionary
files in ispell or MySpell format (as bundled with OpenOffice).

Starting with version 0.9.9-rc1, you can map several source words to
a single destination word. Because the work happens on tokens, not the
source text, differences in whitespace and markup are ignored.

   | core 2 duo > c2d
   | e6600 > c2d
   | core 2duo > c2d

Notice however that the destination wordforms are still always interpreted
as a single keyword! Having a mapping like "St John > Saint John" will
result in not matching "St John" when searching for "Saint" or "John",
because the destination keyword will be "Saint John" with a space character
in it (and it's barely possible to input a destination keyword with
a space).

Example:

   | wordforms = /usr/local/sphinx/data/wordforms.txt

11.2.13. exceptions
-------------------

Tokenizing exceptions file. Optional, default is empty.

Exceptions allow to map one or more tokens (including tokens with
characters that would normally be excluded) to a single keyword. They are
similar to wordforms in that they also perform mapping, but have a number
of important differences.

Short summary of the differences is as follows:

   * exceptions are case sensitive, wordforms are not;
   * exceptions can use special characters that are not in charset_table,
     wordforms fully obey charset_table;
   * exceptions can underperform on huge dictionaries, wordforms handle
     millions of entries well.

The expected file format is also plain text, with one line per exception,
and the line format is as follows:

   | map-from-tokens => map-to-token

Example file:

   | AT & T => AT&T
   | AT&T => AT&T
   | Standarten   Fuehrer => standartenfuhrer
   | Standarten Fuhrer => standartenfuhrer
   | MS Windows => ms windows
   | Microsoft Windows => ms windows
   | C++ => cplusplus
   | c++ => cplusplus
   | C plus plus => cplusplus

All tokens here are case sensitive: they will not be processed by
charset_table rules. Thus, with the example exceptions file above, "At&t"
text will be tokenized as two keywords "at" and "t", because of lowercase
letters. On the other hand, "AT&T" will match exactly and produce single
"AT&T" keyword.

Note that this map-to keyword is a) always interpereted as a single word,
and b) is both case and space sensitive! In our sample, "ms windows" query
will not match the document with "MS Windows" text. The query will be
interpreted as a query for two keywords, "ms" and "windows". And what "MS
Windows" gets mapped to is a single keyword "ms windows", with a space in
the middle. On the other hand, "standartenfuhrer" will retrieve documents
with "Standarten Fuhrer" or "Standarten Fuehrer" contents (capitalized
exactly like this), or any capitalization variant of the keyword itself,
eg. "staNdarTenfUhreR". (It won't catch "standarten fuhrer", however: this
text does not match any of the listed exceptions because of case
sensitivity, and gets indexed as two separate keywords.)

Whitespace in the map-from tokens list matters, but its amount does not.
Any amount of the whitespace in the map-form list will match any other
amount of whitespace in the indexed document or query. For instance,
"AT & T" map-from token will match "AT    &  T" text, whatever the amount
of space in both map-from part and the indexed text. Such text will
therefore be indexed as a special "AT&T" keyword, thanks to the very first
entry from the sample.

Exceptions also allow to capture special characters (that are exceptions
from general charset_table rules; hence the name). Assume that you
generally do not want to treat '+' as a valid character, but still want to
be able search for some exceptions from this rule such as 'C++'. The sample
above will do just that, totally independent of what characters are in the
table and what are not.

Exceptions are applied to raw incoming document and query data during
indexing and searching respectively. Therefore, to pick up changes in the
file it's required to reindex and restart searchd.

Example:

   | exceptions = /usr/local/sphinx/data/exceptions.txt

11.2.14. min_word_len
---------------------

Minimum indexed word length. Optional, default is 1 (index everything).

Only those words that are not shorter than this minimum will be indexed.
For instance, if min_word_len is 4, then 'the' won't be indexed, but 'they'
will be.

Example:

   | min_word_len = 4

11.2.15. charset_type
---------------------

Character set encoding type. Optional, default is 'sbcs'. Known values are
'sbcs' and 'utf-8'.

Different encodings have different methods for mapping their internal
characters codes into specific byte sequences. Two most common methods in
use today are single-byte encoding and UTF-8. Their corresponding
charset_type values are 'sbcs' (stands for Single Byte Character Set) and
'utf-8'. The selected encoding type will be used everywhere where the index
is used: when indexing the data, when parsing the query against this index,
when generating snippets, etc.

Note that while 'utf-8' implies that the decoded values must be treated as
Unicode codepoint numbers, there's a family of 'sbcs' encodings that may in
turn treat different byte values differently, and that should be properly
reflected in your charset_table settings. For example, the same byte value
of 224 (0xE0 hex) maps to different Russian letters depending on whether
koi-8r or windows-1251 encoding is used.

Example:

   | charset_type = utf-8

11.2.16. charset_table
----------------------

Accepted characters table, with case folding rules. Optional, default value
depends on charset_type value.

charset_table is the main workhorse of Sphinx tokenizing process, ie. the
process of extracting keywords from document text or query txet. It
controls what characters are accepted as valid and what are not, and how
the accepted characters should be transformed (eg. should the case be
removed or not).

You can think of charset_table as of a big table that has a mapping for
each and every of 100K+ characters in Unicode (or as of a small
256-character table if you're using SBCS). By default, every character maps
to 0, which means that it does not occur within keywords and should be
treated as a separator. Once mentioned in the table, character is mapped to
some other character (most frequently, either to itself or to a lowercase
letter), and is treated as a valid keyword part.

The expected value format is a commas-separated list of mappings. Two
simplest mappings simply declare a character as valid, and map a single
character to another single character, respectively. But specifying the
whole table in such form would result in bloated and barely manageable
specifications. So there are several syntax shortcuts that let you map
ranges of characters at once. The complete list is as follows:

A->a
   Single char mapping, declares source char 'A' as allowed to occur within
   keywords and maps it to destination char 'a' (but does not declare 'a'
   as allowed).

A..Z->a..z
   Range mapping, declares all chars in source range as allowed and maps
   them to the destination range. Does not declare destination range as
   allowed. Also checks ranges' lengths (the lengths must be equal).

a
   Stray char mapping, declares a character as allowed and maps it to
   itself. Equivalent to a->a single char mapping.

a..z
   Stray range mapping, declares all characters in range as allowed and
   maps them to themselves. Equivalent to a..z->a..z range mapping.

A..Z/2
   Checkerboard range map. Maps every pair of chars to the second char.
   More formally, declares odd characters in range as allowed and maps them
   to the even ones; also declares even characters as allowed and maps them
   to themselves. For instance, A..Z/2 is equivalent to A->B, B->B, C->D,
   D->D, ..., Y->Z, Z->Z. This mapping shortcut is helpful for a number of
   Unicode blocks where uppercase and lowercase letters go in such
   interleaved order instead of contiguous chunks.

Control characters with codes from 0 to 31 are always treated as
separators. Characters with codes 32 to 127, ie. 7-bit ASCII characters,
can be used in the mappings as is. To avoid configuration file encoding
issues, 8-bit ASCII characters and Unicode characters must be specified in
U+xxx form, where 'xxx' is hexadecimal codepoint number. This form can also
be used for 7-bit ASCII characters to encode special ones: eg. use U+20 to
encode space, U+2E to encode dot, U+2C to encode comma.

Example:

   | # 'sbcs' defaults for English and Russian
   | charset_table = 0..9, A..Z->a..z, _, a..z, \
   | 	U+A8->U+B8, U+B8, U+C0..U+DF->U+E0..U+FF, U+E0..U+FF
   | 
   | # 'utf-8' defaults for English and Russian
   | charset_table = 0..9, A..Z->a..z, _, a..z, \
   | 	U+410..U+42F->U+430..U+44F, U+430..U+44F

11.2.17. ignore_chars
---------------------

Ignored characters list. Optional, default is empty.

Useful in the cases when some characters, such as soft hyphenation mark
(U+00AD), should be not just treated as separators but rather fully
ignored. For example, if '-' is simply not in the charset_table, "abc-def"
text will be indexed as "abc" and "def" keywords. On the contrary, if '-'
is added to ignore_chars list, the same text will be indexed as a single
"abcdef" keyword.

The syntax is the same as for charset_table, but it's only allowed to
declare characters, and not allowed to map them. Also, the ignored
characters must not be present in charset_table.

Example:

   | ignore_chars = U+AD

11.2.18. min_prefix_len
-----------------------

Minimum word prefix length to index. Optional, default is 0 (do not index
prefixes).

Prefix indexing allows to implement wildcard searching by 'wordstart*'
wildcards (refer to enable_star option for details on wildcard syntax).
When mininum prefix length is set to a positive number, indexer will index
all the possible keyword prefixes (ie. word beginnings) in addition to the
keywords themselves. Too short prefixes (below the minimum allowed length)
will not be indexed.

For instance, indexing a keyword "example" with min_prefix_len=3 will
result in indexing "exa", "exam", "examp", "exampl" prefixes along with the
word itself. Searches against such index for "exam" will match documents
that contain "example" word, even if they do not contain "exam" on itself.
However, indexing prefixes will make the index grow significantly (because
of many more indexed keywords), and will degrade both indexing and
searching times.

There's no automatic way to rank perfect word matches higher in a prefix
index, but there's a number of tricks to achieve that. First, you can setup
two indexes, one with prefix indexing and one without it, search through
both, and use SetIndexWeights() call to combine weights. Second, you can
enable star-syntax and rewrite your extended-mode queries:

   | # in sphinx.conf
   | enable_star = 1
   | 
   | // in query
   | $cl->Query ( "( keyword | keyword* ) other keywords" );

Example:

   | min_prefix_len = 3

11.2.19. min_infix_len
----------------------

Minimum infix prefix length to index. Optional, default is 0 (do not index
infixes).

Infix indexing allows to implement wildcard searching by 'start*', '*end',
and '*middle*' wildcards (refer to enable_star option for details on
wildcard syntax). When mininum infix length is set to a positive number,
indexer will index all the possible keyword infixes (ie. substrings) in
addition to the keywords themselves. Too short infixes (below the minimum
allowed length) will not be indexed. For instance, indexing a keyword
"test" with min_infix_len=2 will result in indexing "te", "es", "st",
"tes", "est" infixes along with the word itself. Searches against such
index for "es" will match documents that contain "test" word, even if they
do not contain "es" on itself. However, indexing infixes will make the
index grow significantly (because of many more indexed keywords), and will
degrade both indexing and searching times.

There's no automatic way to rank perfect word matches higher in an infix
index, but the same tricks as with prefix indexes can be applied.

Example:

   | min_infix_len = 3

11.2.20. prefix_fields
----------------------

The list of full-text fields to limit prefix indexing to. Optional, default
is empty (index all fields in prefix mode).

Because prefix indexing impacts both indexing and searching performance, it
might be desired to limit it to specific full-text fields only: for
instance, to provide prefix searching through URLs, but not through page
contents. prefix_fields specifies what fields will be prefix-indexed; all
other fields will be indexed in normal mode. The value format is
a comma-separated list of field names.

Example:

   | prefix_fields = url, domain

11.2.21. infix_fields
---------------------

The list of full-text fields to limit infix indexing to. Optional, default
is empty (index all fields in infix mode).

Similar to prefix_fields, but lets you limit infix-indexing to given
fields.

Example:

   | infix_fields = url, domain

11.2.22. enable_star
--------------------

Enables star-syntax (or wildcard syntax) when searching through
prefix/infix indexes. Optional, default is is 0 (do not use wildcard
syntax), for compatibility with 0.9.7. Known values are 0 and 1.

This feature enables "star-syntax", or wildcard syntax, when searching
through indexes which were created with prefix or infix indexing enabled.
It only affects searching; so it can be changed without reindexing by
simply restarting searchd.

The default value is 0, that means to disable star-syntax and treat all
keywords as prefixes or infixes respectively, depending on indexing-time
min_prefix_len and min_infix_len settings. The value of 1 means that star
('*') can be used at the start and/or the end of the keyword. The star will
match zero or more characters.

For example, assume that the index was built with infixes and that
enable_star is 1. Searching should work as follows:

   1. "abcdef" query will match only those documents that contain the exact
      "abcdef" word in them.
   2. "abc*" query will match those documents that contain any words
      starting with "abc" (including the documents which contain the exact
      "abc" word only);
   3. "*cde*" query will match those documents that contain any words which
      have "cde" characters in any part of the word (including the
      documents which contain the exact "cde" word only).
   4. "*def" query will match those documents that contain any words ending
      with "def" (including the documents that contain the exact "def" word
      only).

Example:

   | enable_star = 1

11.2.23. ngram_len
------------------

N-gram lengths for N-gram indexing. Optional, default is 0 (disable n-gram
indexing). Known values are 0 and 1 (other lengths to be implemented).

N-grams provide basic CJK (Chinese, Japanese, Korean) support for
unsegmented texts. The issue with CJK searching is that there could be no
clear separators between the words. Ideally, the texts would be filtered
through a special program called segmenter that would insert separators in
proper locations. However, segmenters are slow and error prone, and it's
common to index contiguous groups of N characters, or n-grams, instead.

When this feature is enabled, streams of CJK characters are indexed as
N-grams. For example, if incoming text is "ABCDEF" (where A to F represent
some CJK characters) and length is 1, in will be indexed as if it was "A
B C D E F". (With length equal to 2, it would produce "AB BC CD DE EF"; but
only 1 is supported at the moment.) Only those characters that are listed
in ngram_chars table will be split this way; other ones will not be
affected.

Note that if search query is segmented, ie. there are separators between
individual words, then wrapping the words in quotes and using extended mode
will resut in proper matches being found even if the text was not
segmented. For instance, assume that the original query is BC DEF. After
wrapping in quotes on the application side, it should look like "BC" "DEF"
(with quotes). This query will be passed to Sphinx and internally split
into 1-grams too, resulting in "B C" "D E F" query, still with quotes that
are the phrase matching operator. And it will match the text even though
there were no separators in the text.

Even if the search query is not segmented, Sphinx should still produce good
results, thanks to phrase based ranking: it will pull closer phrase matches
(which in case of N-gram CJK words can mean closer multi-character word
matches) to the top.

Example:

   | ngram_len = 1

11.2.24. ngram_chars
--------------------

N-gram characters list. Optional, default is empty.

To be used in conjunction with in ngram_len, this list defines characters,
sequences of which are subject to N-gram extraction. Words comprised of
other characters will not be affected by N-gram indexing feature. The value
format is identical to charset_table.

Example:

   | ngram_chars = U+3000..U+2FA1F

11.2.25. phrase_boundary
------------------------

Phrase boundary characters list. Optional, default is empty.

This list controls what characters will be treated as phrase boundaries, in
order to adjust word positions and enable phrase-level search emulation
through proximity search. The syntax is similar to charset_table. Mappings
are not allowed and the boundary characters must not overlap with anything
else.

On phrase boundary, additional word position increment (specified by
phrase_boundary_step) will be added to current word position. This enables
phrase-level searching through proximity queries: words in different
phrases will be guaranteed to be more than phrase_boundary_step distance
away from each other; so proximity search within that distance will be
equivalent to phrase-level search.

Phrase boundary condition will be raised if and only if such character is
followed by a separator; this is to avoid abbreviations such as
S.T.A.L.K.E.R or URLs being treated as several phrases.

Example:

   | phrase_boundary = ., ?, !, U+2026 # horizontal ellipsis

11.2.26. phrase_boundary_step
-----------------------------

Phrase boundary word position increment. Optional, default is 0.

On phrase boundary, current word position will be additionally incremented
by this number. See phrase_boundary for details.

Example:

   | phrase_boundary_step = 100

11.2.27. html_strip
-------------------

Whether to strip HTML markup from incoming full-text data. Optional,
default is 0. Known values are 0 (disable stripping) and 1 (enable
stripping).

Both HTML tags and entities and considered markup and get processed.

HTML tags are removed, their contents (i.e., everything between <P> and
</P>) are left intact by default. You can choose to keep and index
attributes of the tags (e.g., HREF attribute in an A tag, or ALT in an IMG
one). Several well-known inline tags are completely removed, all other tags
are treated as block level and replaced with whitespace. For example,
'te<B>st</B>' text will be indexed as a single keyword 'test', however,
'te<P>st</P>' will be indexed as two keywords 'te' and 'st'. Known inline
tags are as follows: A, B, I, S, U, BASEFONT, BIG, EM, FONT, IMG, LABEL,
SMALL, SPAN, STRIKE, STRONG, SUB, SUP, TT.

HTML entities get decoded and replaced with corresponding UTF-8 characters.
Stripper supports both numeric forms (such as &#239;) and text forms (such
as &oacute; or &nbsp;). All entities as specified by HTML4 standard are
supported.

Stripping does not work with xmlpipe source type (it's suggested to upgrade
to xmlpipe2 anyway). It should work with properly formed HTML and XHTML,
but, just as most browsers, may produce unexpected results on malformed
input (such as HTML with stray <'s or unclosed >'s).

Only the tags themselves, and also HTML comments, are stripped. To strip
the contents of the tags too (eg. to strip embedded scripts), see
html_remove_elements option. There are no restrictions on tag names; ie.
everything that looks like a valid tag start, or end, or a comment will be
stripped.

Example:

   | html_strip = 1

11.2.28. html_index_attrs
-------------------------

A list of markup attributes to index when stripping HTML. Optional, default
is empty (do not index markup attributes).

Specifies HTML markup attributes whose contents should be retained and
indexed even though other HTML markup is stripped. The format is per-tag
enumeration of indexable attributes, as shown in the example below.

Example:

   | html_index_attrs = img=alt,title; a=title;

11.2.29. html_remove_elements
-----------------------------

A list of HTML elements for which to strip contents along with the elements
themselves. Optional, default is empty string (do not strip contents of any
elements).

This feature allows to strip element contents, ie. everything that is
between the opening and the closing tags. It is useful to remove embedded
scripts, CSS, etc. Short tag form for empty elements (ie. <br />) is
properly supported; ie. the text that follows such tag will not be removed.

The value is a comma-separated list of element (tag) names whose contents
should be removed. Tag names are case insensitive.

Example:

   | html_remove_elements = style, script

11.2.30. local
--------------

Local index declaration in the distributed index. Multi-value, optional,
default is empty.

This setting is used to declare local indexes that will be searched when
given distributed index is searched. Many local indexes can be declared per
each distributed index. Any local index can also be mentioned several times
in different distributed indexes.

Note that by default all local indexes will be searched sequentially,
utilizing only 1 CPU or core. To parallelize processing of the local parts
in the distributed index, you should use dist_threads directive, see
Section 11.4.29, <<dist_threads>>.

Before dist_threads, there also was a legacy solution to configure searchd
to query itself instead of using local indexes (refer to Section 11.2.31,
<<agent>> for the details). However, that creates redundant CPU and network
load, and dist_threads is now strongly suggested instead.

Example:

   | local = chunk1
   | local = chunk2

11.2.31. agent
--------------

Remote agent declaration in the distributed index. Multi-value, optional,
default is empty.

This setting is used to declare remote agents that will be searched when
given distributed index is searched. The agents can be thought of as
network pointers that specify host, port, and index names. In the basic
case agents would correspond to remote physical machines. More formally,
that is not always correct: you can point several agents to the same remote
machine; or you can even point agents to the very same single instance of
searchd (in order to utilize many CPUs or cores).

The value format is as follows:

   | agent = specification:remote-indexes-list
   | specification = hostname ":" port | path

Where 'hostname' is remote host name; 'port' is remote TCP port; 'path' is
Unix-domain socket path and 'remote-indexes-list' is a comma-separated list
of remote index names.

All agents will be searched in parallel. However, all indexes specified for
a given agent will be searched sequentially in this agent. This lets you
fine-tune the configuration to the hardware. For instance, if two remote
indexes are stored on the same physical HDD, it's better to configure one
agent with several sequentially searched indexes to avoid HDD steping. If
they are stored on different HDDs, having two agents will be advantageous,
because the work will be fully parallelized. The same applies to CPUs;
though CPU performance impact caused by two processes stepping on each
other is somewhat smaller and frequently can be ignored at all.

On machines with many CPUs and/or HDDs, agents can be pointed to the same
machine to utilize all of the hardware in parallel and reduce query
latency. There is no need to setup several searchd instances for that; it's
legal to configure the instance to contact itself. Here's an example setup,
intended for a 4-CPU machine, that will use up to 4 CPUs in parallel to
process each query:

   | index dist
   | {
   | 	type = distributed
   | 	local = chunk1
   | 	agent = localhost:9312:chunk2
   | 	agent = localhost:9312:chunk3
   | 	agent = localhost:9312:chunk4
   | }

Note how one of the chunks is searched locally and the same instance of
searchd queries itself to launch searches through three other ones in
parallel.

Example:

   | agent = localhost:9312:chunk2 # contact itself
   | agent = /var/run/searchd.s:chunk2
   | agent = searchbox2:9312:chunk3,chunk4 # search remote indexes

11.2.32. agent_blackhole
------------------------

Remote blackhole agent declaration in the distributed index. Multi-value,
optional, default is empty. Introduced in version 0.9.9-rc1.

agent_blackhole lets you fire-and-forget queries to remote agents. That is
useful for debugging (or just testing) production clusters: you can setup
a separate debugging/testing searchd instance, and forward the requests to
this instance from your production master (aggregator) instance without
interfering with production work. Master searchd will attempt to connect
and query blackhole agent normally, but it will neither wait nor process
any responses. Also, all network errors on blackhole agents will be
ignored. The value format is completely identical to regular agent
directive.

Example:

   | agent_blackhole = testbox:9312:testindex1,testindex2

11.2.33. agent_connect_timeout
------------------------------

Remote agent connection timeout, in milliseconds. Optional, default is 1000
(ie. 1 second).

When connecting to remote agents, searchd will wait at most this much time
for connect() call to complete succesfully. If the timeout is reached but
connect() does not complete, and retries are enabled, retry will be
initiated.

Example:

   | agent_connect_timeout = 300

11.2.34. agent_query_timeout
----------------------------

Remote agent query timeout, in milliseconds. Optional, default is 3000 (ie.
3 seconds).

After connection, searchd will wait at most this much time for remote
queries to complete. This timeout is fully separate from connection
timeout; so the maximum possible delay caused by a remote agent equals to
the sum of agent_connection_timeout and agent_query_timeout. Queries will
not be retried if this timeout is reached; a warning will be produced
instead.

Example:

   | agent_query_timeout = 10000 # our query can be long, allow up to 10 sec

11.2.35. preopen
----------------

Whether to pre-open all index files, or open them per each query. Optional,
default is 0 (do not preopen).

This option tells searchd that it should pre-open all index files on
startup (or rotation) and keep them open while it runs. Currently, the
default mode is not to pre-open the files (this may change in the future).
Preopened indexes take a few (currently 2) file descriptors per index.
However, they save on per-query open() calls; and also they are
invulnerable to subtle race conditions that may happen during index
rotation under high load. On the other hand, when serving many indexes
(100s to 1000s), it still might be desired to open the on per-query basis
in order to save file descriptors.

This directive does not affect indexer in any way, it only affects searchd.

Example:

   | preopen = 1

11.2.36. ondisk_dict
--------------------

Whether to keep the dictionary file (.spi) for this index on disk, or
precache it in RAM. Optional, default is 0 (precache in RAM). Introduced in
version 0.9.9-rc1.

The dictionary (.spi) can be either kept on RAM or on disk. The default is
to fully cache it in RAM. That improves performance, but might cause too
much RAM pressure, especially if prefixes or infixes were used. Enabling
ondisk_dict results in 1 additional disk IO per keyword per query, but
reduces memory footprint.

This directive does not affect indexer in any way, it only affects searchd.

Example:

   | ondisk_dict = 1

11.2.37. inplace_enable
-----------------------

Whether to enable in-place index inversion. Optional, default is 0 (use
separate temporary files). Introduced in version 0.9.9-rc1.

inplace_enable greatly reduces indexing disk footprint, at a cost of
slightly slower indexing (it uses around 2x less disk, but yields around
90-95% the original performance).

Indexing involves two major phases. The first phase collects, processes,
and partially sorts documents by keyword, and writes the intermediate
result to temporary files (.tmp*). The second phase fully sorts the
documents, and creates the final index files. Thus, rebuilding a production
index on the fly involves around 3x peak disk footprint: 1st copy for the
intermediate temporary files, 2nd copy for newly constructed copy, and 3rd
copy for the old index that will be serving production queries in the
meantime. (Intermediate data is comparable in size to the final index.)
That might be too much disk footprint for big data collections, and
inplace_enable allows to reduce it. When enabled, it reuses the temporary
files, outputs the final data back to them, and renames them on completion.
However, this might require additional temporary data chunk relocation,
which is where the performance impact comes from.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | inplace_enable = 1

11.2.38. inplace_hit_gap
------------------------

In-place inversion fine-tuning option. Controls preallocated hitlist gap
size. Optional, default is 0. Introduced in version 0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | inplace_hit_gap = 1M

11.2.39. inplace_docinfo_gap
----------------------------

In-place inversion fine-tuning option. Controls preallocated docinfo gap
size. Optional, default is 0. Introduced in version 0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | inplace_docinfo_gap = 1M

11.2.40. inplace_reloc_factor
-----------------------------

In-place inversion fine-tuning option. Controls relocation buffer size
within indexing memory arena. Optional, default is 0.1. Introduced in
version 0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | inplace_reloc_factor = 0.1

11.2.41. inplace_write_factor
-----------------------------

In-place inversion fine-tuning option. Controls in-place write buffer size
within indexing memory arena. Optional, default is 0.1. Introduced in
version 0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | inplace_write_factor = 0.1

11.2.42. index_exact_words
--------------------------

Whether to index the original keywords along with the stemmed/remapped
versions. Optional, default is 0 (do not index). Introduced in version
0.9.9-rc1.

When enabled, index_exact_words forces indexer to put the raw keywords in
the index along with the stemmed versions. That, in turn, enables exact
form operator in the query language to work. This impacts the index size
and the indexing time. However, searching performance is not impacted at
all.

Example:

   | index_exact_words = 1

11.2.43. overshort_step
-----------------------

Position increment on overshort (less that min_word_len) keywords.
Optional, allowed values are 0 and 1, default is 1. Introduced in version
0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | overshort_step = 1

11.2.44. stopword_step
----------------------

Position increment on stopwords. Optional, allowed values are 0 and 1,
default is 1. Introduced in version 0.9.9-rc1.

This directive does not affect searchd in any way, it only affects indexer.

Example:

   | stopword_step = 1

11.2.45. hitless_words
----------------------

Hitless words list. Optional, allowed values are 'all', or a list file
name. Introduced in version 1.10-beta.

By default, Sphinx full-text index stores not only a list of matching
documents for every given keyword, but also a list of its in-document
positions (aka hitlist). Hitlists enables phrase, proximity, strict order
and other advanced types of searching, as well as phrase proximity ranking.
However, hitlists for specific frequent keywords (that can not be stopped
for some reason despite being frequent) can get huge and thus slow to
process while querying. Also, in some cases we might only care about
boolean keyword matching, and never need position-based searching operators
(such as phrase matching) nor phrase ranking.

hitless_words lets you create indexes that either do not have positional
information (hitlists) at all, or skip it for specific keywords.

Hitless index will generally use less space than the respective regular
index (about 1.5x can be expected). Both indexing and searching should be
faster, at a cost of missing positional query and ranking support. When
searching, positional queries (eg. phrase queries) will be automatically
converted to respective non-positional (document-level) or combined
queries. For instance, if keywords "hello" and "world" are hitless, "hello
world" phrase query will be converted to (hello & world) bag-of-words
query, matching all documents that mention either of the keywords but not
necessarily the exact phrase. And if, in addition, keywords "simon" and
"says" are not hitless, "simon says hello world" will be converted to
("simon says" & hello & world) query, matching all documents that contain
"hello" and "world" anywhere in the document, and also "simon says" as an
exact phrase.

Example:

   | hitless_words = all

11.2.46. expand_keywords
------------------------

Expand keywords with exact forms and/or stars when possible. Optional,
default is 0 (do not expand keywords). Introduced in version 1.10-beta.

Queries against indexes with expand_keywords feature enabled are internally
expanded as follows. If the index was built with prefix or infix indexing
enabled, every keyword gets internally replaced with a disjunction of
keyword itself and a respective prefix or infix (keyword with stars). If
the index was built with both stemming and index_exact_words enabled, exact
form is also added. Here's an example that shows how internal expansion
works when all of the above (infixes, stemming, and exact words) are
combined:

   | running -> ( running | *running* | =running )

Expanded queries take naturally longer to complete, but can possibly
improve the search quality, as the documents with exact form matches should
be ranked generally higher than documents with stemmed or infix matches.

Note that the existing query syntax does not allowe to emulate this kind of
expansion, because internal expansion works on keyword level and expands
keywords within phrase or quorum operators too (which is not possible
through the query syntax).

This directive does not affect indexer in any way, it only affects searchd.

Example:

   | expand_keywords = 1

11.2.47. blend_chars
--------------------

Blended characters list. Optional, default is empty. Introduced in version
1.10-beta.

Blended characters are indexed both as separators and valid characters. For
instance, assume that & is configured as blended and AT&T occurs in an
indexed document. Three different keywords will get indexed, namely "at&t",
treating blended characters as valid, plus "at" and "t", treating them as
separators.

Positions for tokens obtained by replacing blended characters with
whitespace are assigned as usual, so regular keywords will be indexed just
as if there was no blend_chars specified at all. An additional token that
mixes blended and non-blended characters will be put at the starting
position. For instance, if the field contents are "AT&T company" occurs in
the very beginning of the text field, "at" will be given position 1, "t"
position 2, "company" positin 3, and "AT&T" will also be given position
1 ("blending" with the opening regular keyword). Thus, querying for either
AT&T or just AT will match that document, and querying for "AT T" as
a phrase also match it. Last but not least, phrase query for "AT&T company"
will also match it, despite the position

Blended characters can overlap with special characters used in query syntax
(think of T-Mobile or @twitter). Where possible, query parser will
automatically handle blended character as blended. For instance, "hello
@twitter" within quotes (a phrase operator) would handle @-sign as blended,
because @-syntax for field operator is not allowed within phrases.
Otherwise, the character would be handled as an operator. So you might want
to escape the keywords.

Starting with version 2.0.1-beta, blended characters can be remapped, so
that multiple different blended characters could be normalized into just
one base form. This is useful when indexing multiple alternative Unicode
codepoints with equivalent glyphs.

Example:

   | blend_chars = +, &, U+23
   | blend_chars = +, &->+ # 2.0.1 and above

11.2.48. blend_mode
-------------------

Blended tokens indexing mode. Optional, default is trim_none. Introduced in
version 2.0.1-beta.

By default, tokens that mix blended and non-blended characters get indexed
in there entirety. For instance, when both at-sign and an exclamation are
in blend_chars, "@dude!" will get result in two tokens indexed: "@dude!"
(with all the blended characters) and "dude" (without any). Therefore
"@dude" query will not match it.

blend_mode directive adds flexibility to this indexing behavior. It takes
a comma-separated list of options.

   | blend_mode = option [, option [, ...]]
   | option = trim_none | trim_head | trim_tail | trim_both | skip_pure

Options specify token indexing variants. If multiple options are specified,
multiple variants of the same token will be indexed. Regular keywords
(resulting from that token by replacing blended with whitespace) are always
be indexed.

trim_none
   Index the entire token.

trim_head
   Trim heading blended characters, and index the resulting token.

trim_tail
   Trim trailing blended characters, and index the resulting token.

trim_both
   Trim both heading and trailing blended characters, and index the
   resulting token.

skip_pure
   Do not index the token if it's purely blended, that is, consists of
   blended characters only.

Returning to the "@dude!" example above, setting blend_mode = trim_head,
trim_tail will result in two tokens being indexed, "@dude" and "dude!". In
this particular example, trim_both would have no effect, because trimming
both blended characters results in "dude" which is already indexed as
a regular keyword. Indexing "@U.S.A." with trim_both (and assuming that dot
is blended two) would result in "U.S.A" being indexed. Last but not least,
skip_pure enables you to fully ignore sequences of blended characters only.
For example, "one @@@ two" would be indexed exactly as "one two", and match
that as a phrase. That is not the case by default because a fully blended
token gets indexed and offsets the second keyword position.

Default behavior is to index the entire token, equivalent to blend_mode =
trim_none.

Example:

   | blend_mode = trim_tail, skip_pure

11.2.49. rt_mem_limit
---------------------

RAM chunk size limit. Optional, default is empty. Introduced in version
1.10-beta.

RT index keeps some data in memory (so-called RAM chunk) and also maintains
a number of on-disk indexes (so-called disk chunks). This directive lets
you control the RAM chunk size. Once there's too much data to keep in RAM,
RT index will flush it to disk, activate a newly created disk chunk, and
reset the RAM chunk.

The limit is pretty strict; RT index should never allocate more memory than
it's limited to. The memory is not preallocated either, hence, specifying
512 MB limit and only inserting 3 MB of data should result in allocating
3 MB, not 512 MB.

Example:

   | rt_mem_limit = 512M

11.2.50. rt_field
-----------------

Full-text field declaration. Multi-value, mandatory Introduced in version
1.10-beta.

Full-text fields to be indexed are declared using rt_field directive. The
names must be unique. The order is preserved; and so field values in INSERT
statements without an explicit list of inserted columns will have to be in
the same order as configured.

Example:

   | rt_field = author
   | rt_field = title
   | rt_field = content

11.2.51. rt_attr_uint
---------------------

Unsigned integer attribute declaration. Multi-value (an arbitrary number of
attributes is allowed), optional. Declares an unsigned 32-bit attribute.
Introduced in version 1.10-beta.

Example:

   | rt_attr_uint = gid

11.2.52. rt_attr_bigint
-----------------------

BIGINT attribute declaration. Multi-value (an arbitrary number of
attributes is allowed), optional. Declares a signed 64-bit attribute.
Introduced in version 1.10-beta.

Example:

   | rt_attr_bigint = guid

11.2.53. rt_attr_float
----------------------

Floating point attribute declaration. Multi-value (an arbitrary number of
attributes is allowed), optional. Declares a single precision, 32-bit IEEE
754 format float attribute. Introduced in version 1.10-beta.

Example:

   | rt_attr_float = gpa

11.2.54. rt_attr_multi
----------------------

Multi-valued attribute (MVA) declaration. Declares the UNSIGNED INTEGER
(unsigned 32-bit) MVA attribute. Multi-value (ie. there may be more than
one such attribute declared), optional. Applies to RT indexes only.

Example:

   | rt_attr_multi = my_tags

11.2.55. rt_attr_multi_64
-------------------------

Multi-valued attribute (MVA) declaration. Declares the BIGINT (signed
64-bit) MVA attribute. Multi-value (ie. there may be more than one such
attribute declared), optional. Applies to RT indexes only.

Example:

   | rt_attr_multi_64 = my_wide_tags

11.2.56. rt_attr_timestamp
--------------------------

Timestamp attribute declaration. Multi-value (an arbitrary number of
attributes is allowed), optional. Introduced in version 1.10-beta.

Example:

   | rt_attr_timestamp = date_added

11.2.57. rt_attr_string
-----------------------

String attribute declaration. Multi-value (an arbitrary number of
attributes is allowed), optional. Introduced in version 1.10-beta.

Example:

   | rt_attr_string = author

11.3. indexer program configuration options
===========================================

11.3.1. mem_limit
-----------------

Indexing RAM usage limit. Optional, default is 32M.

Enforced memory usage limit that the indexer will not go above. Can be
specified in bytes, or kilobytes (using K postfix), or megabytes (using
M postfix); see the example. This limit will be automatically raised if set
to extremely low value causing I/O buffers to be less than 8 KB; the exact
lower bound for that depends on the indexed data size. If the buffers are
less than 256 KB, a warning will be produced.

Maximum possible limit is 2047M. Too low values can hurt indexing speed,
but 256M to 1024M should be enough for most if not all datasets. Setting
this value too high can cause SQL server timeouts. During the document
collection phase, there will be periods when the memory buffer is partially
sorted and no communication with the database is performed; and the
database server can timeout. You can resolve that either by raising
timeouts on SQL server side or by lowering mem_limit.

Example:

   | mem_limit = 256M
   | # mem_limit = 262144K # same, but in KB
   | # mem_limit = 268435456 # same, but in bytes

11.3.2. max_iops
----------------

Maximum I/O operations per second, for I/O throttling. Optional, default is
0 (unlimited).

I/O throttling related option. It limits maximum count of I/O operations
(reads or writes) per any given second. A value of 0 means that no limit is
imposed.

indexer can cause bursts of intensive disk I/O during indexing, and it
might desired to limit its disk activity (and keep something for other
programs running on the same machine, such as searchd). I/O throttling
helps to do that. It works by enforcing a minimum guaranteed delay between
subsequent disk I/O operations performed by indexer. Modern SATA HDDs are
able to perform up to 70-100+ I/O operations per second (that's mostly
limited by disk heads seek time). Limiting indexing I/O to a fraction of
that can help reduce search performance dedgradation caused by indexing.

Example:

   | max_iops = 40

11.3.3. max_iosize
------------------

Maximum allowed I/O operation size, in bytes, for I/O throttling. Optional,
default is 0 (unlimited).

I/O throttling related option. It limits maximum file I/O operation (read
or write) size for all operations performed by indexer. A value of 0 means
that no limit is imposed. Reads or writes that are bigger than the limit
will be split in several smaller operations, and counted as several
operation by max_iops setting. At the time of this writing, all I/O calls
should be under 256 KB (default internal buffer size) anyway, so max_iosize
values higher than 256 KB must not affect anything.

Example:

   | max_iosize = 1048576

11.3.4. max_xmlpipe2_field
--------------------------

Maximum allowed field size for XMLpipe2 source type, bytes. Optional,
default is 2 MB.

Example:

   | max_xmlpipe2_field = 8M

11.3.5. write_buffer
--------------------

Write buffer size, bytes. Optional, default is 1 MB.

Write buffers are used to write both temporary and final index files when
indexing. Larger buffers reduce the number of required disk writes. Memory
for the buffers is allocated in addition to mem_limit. Note that several
(currently up to 4) buffers for different files will be allocated,
proportionally increasing the RAM usage.

Example:

   | write_buffer = 4M

11.3.6. max_file_field_buffer
-----------------------------

Maximum file field adaptive buffer size, bytes. Optional, default is 8 MB,
minimum is 1 MB.

File field buffer is used to load files referred to from sql_file_field
columns. This buffer is adaptive, starting at 1 MB at first allocation, and
growing in 2x steps until either file contents can be loaded, or maximum
buffer size, specified by max_file_field_buffer directive, is reached.

Thus, if there are no file fields are specified, no buffer is allocated at
all. If all files loaded during indexing are under (for example) 2 MB in
size, but max_file_field_buffer value is 128 MB, peak buffer usage would
still be only 2 MB. However, files over 128 MB would be entirely skipped.

Example:

   | max_file_field_buffer = 128M

11.3.7. on_file_field_error
---------------------------

How to handle IO errors in file fields. Optional, default is ignore_field.
Introduced in version 2.0.2-beta.

When there is a problem indexing a file referenced by a file field
(Section 11.1.29, <<sql_file_field>>), indexer can either index the
document, assuming empty content in this particular field, or skip the
document, or fail indexing entirely. on_file_field_error directive controls
that behavior. The values it takes are:

   * ignore_field, index the current document without field;
   * skip_document, skip the current document but continue indexing;
   * fail_index, fail indexing with an error message.

The problems that can arise are: open error, size error (file too big), and
data read error. Warning messages on any problem will be given at all
times, irregardless of the phase and the on_file_field_error setting.

Note that with on_file_field_error = skip_document documents will only be
ignored if problems are detected during an early check phase, and not
during the actual file parsing phase. indexer will open every referenced
file and check its size before doing any work, and then open it again when
doing actual parsing work. So in case a file goes away between these two
open attempts, the document will still be indexed.

Example:

   | on_file_field_errors = skip_document

11.4. searchd program configuration options
===========================================

11.4.1. listen
--------------

This setting lets you specify IP address and port, or Unix-domain socket
path, that searchd will listen on. Introduced in version 0.9.9-rc1.

The informal grammar for listen setting is:

   | listen = ( address ":" port | port | path ) [ ":" protocol ]

I.e. you can specify either an IP address (or hostname) and port number, or
just a port number, or Unix socket path. If you specify port number but not
the address, searchd will listen on all network interfaces. Unix path is
identified by a leading slash.

Starting with version 0.9.9-rc2, you can also specify a protocol handler
(listener) to be used for connections on this socket. Supported protocol
values are 'sphinx' (Sphinx 0.9.x API protocol) and 'mysql41' (MySQL
protocol used since 4.1 upto at least 5.1). More details on MySQL protocol
support can be found in Section 5.10, <<MySQL protocol support and
SphinxQL>> section.

Examples:

   | listen = localhost
   | listen = localhost:5000
   | listen = 192.168.0.1:5000
   | listen = /var/run/sphinx.s
   | listen = 9312
   | listen = localhost:9306:mysql41

There can be multiple listen directives, searchd will listen for client
connections on all specified ports and sockets. If no listen directives are
found then the server will listen on all available interfaces using the
default SphinxAPI port 9312. Starting with 1.10-beta, it will also listen
on default SphinxQL port 9306. Both port numbers are assigned by IANA (see
http://www.iana.org/assignments/port-numbers for details) and should
therefore be available.

Unix-domain sockets are not supported on Windows.

11.4.2. address
---------------

Interface IP address to bind on. Optional, default is 0.0.0.0 (ie. listen
on all interfaces). DEPRECATED, use listen instead.

address setting lets you specify which network interface searchd will bind
to, listen on, and accept incoming network connections on. The default
value is 0.0.0.0 which means to listen on all interfaces. At the time, you
can not specify multiple interfaces.

Example:

   | address = 192.168.0.1

11.4.3. port
------------

searchd TCP port number. DEPRECATED, use listen instead. Used to be
mandatory. Default port number is 9312.

Example:

   | port = 9312

11.4.4. log
-----------

Log file name. Optional, default is 'searchd.log'. All searchd run time
events will be logged in this file.

Also you can use the 'syslog' as the file name. In this case the events
will be sent to syslog daemon. To use the syslog option the sphinx must be
configured '--with-syslog' on building.

Example:

   | log = /var/log/searchd.log

11.4.5. query_log
-----------------

Query log file name. Optional, default is empty (do not log queries). All
search queries will be logged in this file. The format is described in
Section 5.9, <<searchd query log formats>>.

In case of 'plain' format, you can use the 'syslog' as the path to the log
file. In this case all search queries will be sent to syslog daemon with
LOG_INFO priority, prefixed with '[query]' instead of timestamp. To use the
syslog option the sphinx must be configured '--with-syslog' on building.

Example:

   | query_log = /var/log/query.log

11.4.6. query_log_format
------------------------

Query log format. Optional, allowed values are 'plain' and 'sphinxql',
default is 'plain'. Introduced in version 2.0.1-beta.

Starting with version 2.0.1-beta, two different log formats are supported.
The default one logs queries in a custom text format. The new one logs
valid SphinxQL statements. This directive allows to switch between the two
formats on search daemon startup. The log format can also be altered on the
fly, using SET GLOBAL query_log_format=sphinxql syntax. Refer to
Section 5.9, <<searchd query log formats>> for more discussion and format
details.

Example:

   | query_log_format = sphinxql

11.4.7. read_timeout
--------------------

Network client request read timeout, in seconds. Optional, default is
5 seconds. searchd will forcibly close the client connections which fail to
send a query within this timeout.

Example:

   | read_timeout = 1

11.4.8. client_timeout
----------------------

Maximum time to wait between requests (in seconds) when using persistent
connections. Optional, default is five minutes.

Example:

   | client_timeout = 3600

11.4.9. max_children
--------------------

Maximum amount of children to fork (or in other words, concurrent searches
to run in parallel). Optional, default is 0 (unlimited).

Useful to control server load. There will be no more than this much
concurrent searches running, at all times. When the limit is reached,
additional incoming clients are dismissed with temporarily failure
(SEARCHD_RETRY) status code and a message stating that the server is maxed
out.

Example:

   | max_children = 10

11.4.10. pid_file
-----------------

searchd process ID file name. Mandatory.

PID file will be re-created (and locked) on startup. It will contain head
daemon process ID while the daemon is running, and it will be unlinked on
daemon shutdown. It's mandatory because Sphinx uses it internally for
a number of things: to check whether there already is a running instance of
searchd; to stop searchd; to notify it that it should rotate the indexes.
Can also be used for different external automation scripts.

Example:

   | pid_file = /var/run/searchd.pid

11.4.11. max_matches
--------------------

Maximum amount of matches that the daemon keeps in RAM for each index and
can return to the client. Optional, default is 1000.

Introduced in order to control and limit RAM usage, max_matches setting
defines how much matches will be kept in RAM while searching each index.
Every match found will still be processed; but only best N of them will be
kept in memory and return to the client in the end. Assume that the index
contains 2,000,000 matches for the query. You rarely (if ever) need to
retrieve all of them. Rather, you need to scan all of them, but only choose
"best" at most, say, 500 by some criteria (ie. sorted by relevance, or
price, or anything else), and display those 500 matches to the end user in
pages of 20 to 100 matches. And tracking only the best 500 matches is much
more RAM and CPU efficient than keeping all 2,000,000 matches, sorting
them, and then discarding everything but the first 20 needed to display the
search results page. max_matches controls N in that "best N" amount.

This parameter noticeably affects per-query RAM and CPU usage. Values of
1,000 to 10,000 are generally fine, but higher limits must be used with
care. Recklessly raising max_matches to 1,000,000 means that searchd will
have to allocate and initialize 1-million-entry matches buffer for every
query. That will obviously increase per-query RAM usage, and in some cases
can also noticeably impact performance.

CAVEAT EMPTOR! Note that there also is another place where this limit is
enforced. max_matches can be decreased on the fly through the corresponding
API call, and the default value in the API is also set to 1,000. So in
order to retrieve more than 1,000 matches to your application, you will
have to change the configuration file, restart searchd, and set proper
limit in SetLimits() call. Also note that you can not set the value in the
API higher than the value in the .conf file. This is prohibited in order to
have some protection against malicious and/or malformed requests.

Example:

   | max_matches = 10000

11.4.12. seamless_rotate
------------------------

Prevents searchd stalls while rotating indexes with huge amounts of data to
precache. Optional, default is 1 (enable seamless rotation).

Indexes may contain some data that needs to be precached in RAM. At the
moment, .spa, .spi and .spm files are fully precached (they contain
attribute data, MVA data, and keyword index, respectively.) Without
seamless rotate, rotating an index tries to use as little RAM as possible
and works as follows:

   1. new queries are temporarly rejected (with "retry" error code);
   2. searchd waits for all currently running queries to finish;
   3. old index is deallocated and its files are renamed;
   4. new index files are renamed and required RAM is allocated;
   5. new index attribute and dictionary data is preloaded to RAM;
   6. searchd resumes serving queries from new index.

However, if there's a lot of attribute or dictionary data, then preloading
step could take noticeble time - up to several minutes in case of
preloading 1-5+ GB files.

With seamless rotate enabled, rotation works as follows:

   1. new index RAM storage is allocated;
   2. new index attribute and dictionary data is asynchronously preloaded
      to RAM;
   3. on success, old index is deallocated and both indexes' files are
      renamed;
   4. on failure, new index is deallocated;
   5. at any given moment, queries are served either from old or new index
      copy.

Seamless rotate comes at the cost of higher peak memory usage during the
rotation (because both old and new copies of .spa/.spi/.spm data need to be
in RAM while preloading new copy). Average usage stays the same.

Example:

   | seamless_rotate = 1

11.4.13. preopen_indexes
------------------------

Whether to forcibly preopen all indexes on startup. Optional, default is
1 (preopen everything).

Starting with 2.0.1-beta, the default value for this option is now
1 (foribly preopen all indexes). In prior versions, it used to be 0 (use
per-index settings).

When set to 1, this directive overrides and enforces preopen on all
indexes. They will be preopened, no matter what is the per-index preopen
setting. When set to 0, per-index settings can take effect. (And they
default to 0.)

Pre-opened indexes avoid races between search queries and rotations that
can cause queries to fail occasionally. They also make searchd use more
file handles. In most scenarios it's therefore preferred and recommended to
preopen indexes.

Example:

   | preopen_indexes = 1

11.4.14. unlink_old
-------------------

Whether to unlink .old index copies on succesful rotation. Optional,
default is 1 (do unlink).

Example:

   | unlink_old = 0

11.4.15. attr_flush_period
--------------------------

When calling UpdateAttributes() to update document attributes in real-time,
changes are first written to the in-memory copy of attributes (docinfo must
be set to extern). Then, once searchd shuts down normally (via SIGTERM
being sent), the changes are written to disk. Introduced in version
0.9.9-rc1.

Starting with 0.9.9-rc1, it is possible to tell searchd to periodically
write these changes back to disk, to avoid them being lost. The time
between those intervals is set with attr_flush_period, in seconds.

It defaults to 0, which disables the periodic flushing, but flushing will
still occur at normal shut-down.

Example:

   | attr_flush_period = 900 # persist updates to disk every 15 minutes

11.4.16. ondisk_dict_default
----------------------------

Instance-wide defaults for ondisk_dict directive. Optional, default it
0 (precache dictionaries in RAM). Introduced in version 0.9.9-rc1.

This directive lets you specify the default value of ondisk_dict for all
the indexes served by this copy of searchd. Per-index directive take
precedence, and will overwrite this instance-wide default value, allowing
for fine-grain control.

Example:

   | ondisk_dict_default = 1 # keep all dictionaries on disk

11.4.17. max_packet_size
------------------------

Maximum allowed network packet size. Limits both query packets from
clients, and response packets from remote agents in distributed
environment. Only used for internal sanity checks, does not directly affect
RAM use or performance. Optional, default is 8M. Introduced in version
0.9.9-rc1.

Example:

   | max_packet_size = 32M

11.4.18. mva_updates_pool
-------------------------

Shared pool size for in-memory MVA updates storage. Optional, default size
is 1M. Introduced in version 0.9.9-rc1.

This setting controls the size of the shared storage pool for updated MVA
values. Specifying 0 for the size disable MVA updates at all. Once the pool
size limit is hit, MVA update attempts will result in an error. However,
updates on regular (scalar) attributes will still work. Due to internal
technical difficulties, currently it is not possible to store (flush) any
updates on indexes where MVA were updated; though this might be implemented
in the future. In the meantime, MVA updates are intended to be used as
a measure to quickly catchup with latest changes in the database until the
next index rebuild; not as a persistent storage mechanism.

Example:

   | mva_updates_pool = 16M

11.4.19. crash_log_path
-----------------------

Deprecated debugging setting, path (formally prefix) for crash log files.
Introduced in version 0.9.9-rc1. Deprecated in version 2.0.1-beta, as crash
debugging information now gets logged into searchd.log in text form, and
separate binary crash logs are no longer needed.

11.4.20. max_filters
--------------------

Maximum allowed per-query filter count. Only used for internal sanity
checks, does not directly affect RAM use or performance. Optional, default
is 256. Introduced in version 0.9.9-rc1.

Example:

   | max_filters = 1024

11.4.21. max_filter_values
--------------------------

Maximum allowed per-filter values count. Only used for internal sanity
checks, does not directly affect RAM use or performance. Optional, default
is 4096. Introduced in version 0.9.9-rc1.

Example:

   | max_filter_values = 16384

11.4.22. listen_backlog
-----------------------

TCP listen backlog. Optional, default is 5.

Windows builds currently (as of 0.9.9) can only process the requests one by
one. Concurrent requests will be enqueued by the TCP stack on OS level, and
requests that can not be enqueued will immediately fail with "connection
refused" message. listen_backlog directive controls the length of the
connection queue. Non-Windows builds should work fine with the default
value.

Example:

   | listen_backlog = 20

11.4.23. read_buffer
--------------------

Per-keyword read buffer size. Optional, default is 256K.

For every keyword occurrence in every search query, there are two
associated read buffers (one for document list and one for hit list). This
setting lets you control their sizes, increasing per-query RAM use, but
possibly decreasing IO time.

Example:

   | read_buffer = 1M

11.4.24. read_unhinted
----------------------

Unhinted read size. Optional, default is 32K.

When querying, some reads know in advance exactly how much data is there to
be read, but some currently do not. Most prominently, hit list size in not
currently known in advance. This setting lest you control how much data to
read in such cases. It will impact hit list IO time, reducing it for lists
larger than unhinted read size, but raising it for smaller lists. It will
not affect RAM use because read buffer will be already allocated. So it
should be not greater than read_buffer.

Example:

   | read_unhinted = 32K

11.4.25. max_batch_queries
--------------------------

Limits the amount of queries per batch. Optional, default is 32.

Makes searchd perform a sanity check of the amount of the queries submitted
in a single batch when using multi-queries. Set it to 0 to skip the check.

Example:

   | max_batch_queries = 256

11.4.26. subtree_docs_cache
---------------------------

Max common subtree document cache size, per-query. Optional, default is
0 (disabled).

Limits RAM usage of a common subtree optimizer (see Section 5.11,
<<Multi-queries>>). At most this much RAM will be spent to cache document
entries per each query. Setting the limit to 0 disables the optimizer.

Example:

   | subtree_docs_cache = 8M

11.4.27. subtree_hits_cache
---------------------------

Max common subtree hit cache size, per-query. Optional, default is
0 (disabled).

Limits RAM usage of a common subtree optimizer (see Section 5.11,
<<Multi-queries>>). At most this much RAM will be spent to cache keyword
occurrences (hits) per each query. Setting the limit to 0 disables the
optimizer.

Example:

   | subtree_hits_cache = 16M

11.4.28. workers
----------------

Multi-processing mode (MPM). Optional; allowed values are none, fork,
prefork, and threads. Default is fork on Unix based systems, and threads on
Windows. Introduced in version 1.10-beta.

Lets you choose how searchd processes multiple concurrent requests. The
possible values are:

none
   All requests will be handled serially, one-by-one. Prior to 1.x, this
   was the only mode available on Windows.

fork
   A new child process will be forked to handle every incoming request.
   Historically, this is the default mode.

prefork
   On startup, searchd will pre-fork a number of worker processes, and pass
   the incoming requests to one of those children.

threads
   A new thread will be created to handle every incoming request. This is
   the only mode compatible with RT indexing backend.

Historically, searchd used fork-based model, which generally performs OK
but spends a noticeable amount of CPU in fork() system call when there's
a high amount of (tiny) requests per second. Prefork mode was implemented
to alleviate that; with prefork, worker processes are basically only
created on startup and re-created on index rotation, somewhat reducing
fork() call pressure.

Threads mode was implemented along with RT backend and is required to use
RT indexes. (Regular disk-based indexes work in all the available modes.)

Example:

   | workers = threads

11.4.29. dist_threads
---------------------

Max local worker threads to use for parallelizable requests (searching
a distributed index; building a batch of snippets). Optional, default is 0,
which means to disable in-request parallelism. Introduced in version
1.10-beta.

Distributed index can include several local indexes. dist_threads lets you
easily utilize multiple CPUs/cores for that (previously existing
alternative was to specify the indexes as remote agents, pointing searchd
to itself and paying some network overheads).

When set to a value N greater than 1, this directive will create up to
N threads for every query, and schedule the specific searches within these
threads. For example, if there are 7 local indexes to search and
dist_threads is set to 2, then 2 parallel threads would be created: one
that sequentially searches 4 indexes, and another one that searches the
other 3 indexes.

In case of CPU bound workload, setting dist_threads to 1x the number of
cores is advised (creating more threads than cores will not improve query
time). In case of mixed CPU/disk bound workload it might sometimes make
sense to use more (so that all cores could be utilizes even when there are
threads that wait for I/O completion).

Note that dist_threads does not require threads MPM. You can perfectly use
it with fork or prefork MPMs too.

Starting with version 2.0.1-beta, building a batch of snippets with
load_files flag enabled can also be parallelized. Up to dist_threads
threads are be created to process those files. That speeds up snippet
extraction when the total amount of document data to process is significant
(hundreds of megabytes).

Example:

   | index dist_test
   | {
   | 	type = distributed
   | 	local = chunk1
   | 	local = chunk2
   | 	local = chunk3
   | 	local = chunk4
   | }
   | 
   | # ...
   | 
   | dist_threads = 4

11.4.30. binlog_path
--------------------

Binary log (aka transaction log) files path. Optional, default is
build-time configured data directory. Introduced in version 1.10-beta.

Binary logs are used for crash recovery of RT index data, and also of
attributes updates of plain disk indices that would otherwise only be
stored in RAM untill flush. When logging is enabled, every transaction
COMMIT-ted into RT index gets written into a log file. Logs are then
automatically replayed on startup after an unclean shutdown, recovering the
logged changes.

binlog_path directive specifies the binary log files location. It should
contain just the path; searchd will create and unlink multiple binlog.*
files in that path as necessary (binlog data, metadata, and lock files,
etc).

Empty value disables binary logging. That improves performance, but puts RT
index data at risk.

WARNING! It is strongly recommended to always explicitly define
'binlog_path' option in your config. Otherwise, the default path, which in
most cases is the same as working folder, may point to the folder with no
write access (for example, /usr/local/var/data). In this case, the searchd
will not start at all.

Example:

   | binlog_path = # disable logging
   | binlog_path = /var/data # /var/data/binlog.001 etc will be created

11.4.31. binlog_flush
---------------------

Binary log transaction flush/sync mode. Optional, default is 2 (flush every
transaction, sync every second). Introduced in version 1.10-beta.

This directive controls how frequently will binary log be flushed to OS and
synced to disk. Three modes are supported:

   * 0, flush and sync every second. Best performance, but up to 1 second
     worth of committed transactions can be lost both on daemon crash, or
     OS/hardware crash.
   * 1, flush and sync every transaction. Worst performance, but every
     committed transaction data is guaranteed to be saved.
   * 2, flush every transaction, sync every second. Good performance, and
     every committed transaction is guaranteed to be saved in case of
     daemon crash. However, in case of OS/hardware crash up to 1 second
     worth of committed transactions can be lost.

For those familiar with MySQL and InnoDB, this directive is entirely
similar to innodb_flush_log_at_trx_commit. In most cases, the default
hybrid mode 2 provides a nice balance of speed and safety, with full RT
index data protection against daemon crashes, and some protection against
hardware ones.

Example:

   | binlog_flush = 1 # ultimate safety, low speed

11.4.32. binlog_max_log_size
----------------------------

Maximum binary log file size. Optional, default is 0 (do not reopen binlog
file based on size). Introduced in version 1.10-beta.

A new binlog file will be forcibly opened once the current binlog file
reaches this limit. This achieves a finer granularity of logs and can yield
more efficient binlog disk usage under certain borderline workloads.

Example:

   | binlog_max_log_size = 16M

11.4.33. collation_server
-------------------------

Default server collation. Optional, default is libc_ci. Introduced in
version 2.0.1-beta.

Specifies the default collation used for incoming requests. The collation
can be overridden on a per-query basis. Refer to Section 5.12,
<<Collations>> section for the list of available collations and other
details.

Example:

   | collation_server = utf8_ci

11.4.34. collation_libc_locale
------------------------------

Server libc locale. Optional, default is C. Introduced in version
2.0.1-beta.

Specifies the libc locale, affecting the libc-based collations. Refer to
Section 5.12, <<Collations>> section for the details.

Example:

   | collation_libc_locale = fr_FR

11.4.35. plugin_dir
-------------------

Trusted location for the dynamic libraries (UDFs). Optional, default is
empty (no location). Introduced in version 2.0.1-beta.

Specifies the trusted directory from which the UDF libraries can be loaded.
Requires workers = thread to take effect.

Example:

   | workers = threads
   | plugin_dir = /usr/local/sphinx/lib

11.4.36. mysql_version_string
-----------------------------

A server version string to return via MySQL protocol. Optional, default is
empty (return Sphinx version). Introduced in version 2.0.1-beta.

Several picky MySQL client libraries depend on a particular version number
format used by MySQL, and moreover, sometimes choose a different execution
path based on the reported version number (rather than the indicated
capabilities flags). For instance, Python MySQLdb 1.2.2 throws an exception
when the version number is not in X.Y.ZZ format; MySQL .NET connector 6.3.x
fails internally on version numbers 1.x along with a certain combination of
flags, etc. To workaround that, you can use mysql_version_string directive
and have searchd report a different version to clients connecting over
MySQL protocol. (By default, it reports its own version.)

Example:

   | mysql_version_string = 5.0.37

11.4.37. rt_flush_period
------------------------

RT indexes RAM chunk flush check period, in seconds. Optional, default is
0 (do not flush). Introduced in version 2.0.1-beta.

Actively updated RT indexes that however fully fit in RAM chunks can result
in ever-growing binlogs, impacting disk use and crash recovery time. With
this directive the search daemon performs periodic flush checks, and
eligible RAM chunks can get saved, enabling consequential binlog cleanup.
See Section 4.4, <<Binary logging>> for more details.

Example:

   | rt_flush_period = 3600

11.4.38. thread_stack
---------------------

Per-thread stack size. Optional, default is 64K. Introduced in version
2.0.1-beta.

In the workers = threads mode, every request is processed with a separate
thread that needs its own stack space. By default, 64K per thread are
allocated for stack. However, extremely complex search requests might
eventually exhaust the default stack and require more. For instance,
a query that matches a few thousand keywords (either directly or through
term expansion) can eventually run out of stack. Previously, that resulted
in crashes. Starting with 2.0.1-beta, searchd attempts to estimate the
expected stack use, and blocks the potentially dangerous queries. To
process such queries, you can either the thread stack size by using the
thread_stack directive (or switch to a different workers setting if that is
possible).

A query with N levels of nesting is estimated to require approximately
30+0.12*N KB of stack, meaning that the default 64K is enough for queries
with upto 300 levels, 150K for upto 1000 levels, etc. If the stack size
limit is not met, searchd fails the query and reports the required stack
size in the error message.

Example:

   | thread_stack = 256K

11.4.39. expansion_limit
------------------------

The maximum number of expanded keywords for a single wildcard. Optional,
default is 0 (no limit). Introduced in version 2.0.1-beta.

When doing substring searches against indexes built with dict = keywords
enabled, a single wildcard may potentially result in thousands and even
millions of matched keywords (think of matching 'a*' against the entire
Oxford dictionary). This directive lets you limit the impact of such
expansions. Setting expansion_limit = N restricts expansions to no more
than N of the most frequent matching keywords (per each wildcard in the
query).

Example:

   | expansion_limit = 16

11.4.40. compat_sphinxql_magics
-------------------------------

Legacy SphinxQL quirks compatiblity mode. Optional, default is 1 (keep
compatibility). Introduced in version 2.0.1-beta.

Starting with version 2.0.1-beta, we're bringing SphinxQL in closer
compliance with standard SQL. However, existing applications must not get
broken, and compat_sphinxql_magics lets you upgrade safely. It defauls to
1, which enables the compatibility mode. However, SphinxQL compatibility
mode is now deprecated and will be removed once we complete bringing
SphinxQL in line with standard SQL syntax. So it's advised to update the
applications utilising SphinxQL and then switch the daemon to the new, more
SQL compliant mode by setting compat_sphinxql_magics = 0. Please refer to
Section 7.24, <<SphinxQL upgrade notes, version 2.0.1-beta>> for the
details and update instruction.

Example:

   | compat_sphinxql_magics = 0 # the future is now

11.4.41. watchdog
-----------------

Threaded server watchdog. Optional, default is 1 (watchdog enabled).
Introduced in version 2.0.1-beta.

A crashed query in threads multi-processing mode (workers = threads) can
take down the entire server. With watchdog feature enabled, searchd
additionally keeps a separate lightweight process that monitors the main
server process, and automatically restarts the latter in case of abnormal
termination. Watchdog is enabled by default.

Example:

   | watchdog = 0 # disable watchdog

11.4.42. prefork_rotation_throttle
----------------------------------

Delay between restarting preforked children on index rotation, in
milliseconds. Optional, default is 0 (no delay). Introduced in version
2.0.2-beta.

When running in workers = prefork mode, every index rotation needs to
restart all children to propagate the newly loaded index data changes.
Restarting all of them at once might put excessive strain on CPU and/or
network connections. (For instance, when the application keeps a bunch of
open persistent connections to different children, and all those children
restart.) Those bursts can be throttled down with prefork_rotation_throttle
directive. Note that the children will be restarted sequentially, and thus
"old" results might persist for a few more seconds. For instance, if
prefork_rotation_throttle is set to 50 (milliseconds), and there are 30
children, then the last one would only be actually restarted 1.5 seconds
(50*30=1500 milliseconds) after the "rotation finished" message in the
searchd event log.

Example:

   | prefork_rotation_throttle = 50 # throttle children restarts by 50 msec each

Appendix A. Sphinx revision history
===================================

Table of Contents

A.1. Version 2.0.8-release, 26 apr 2013
A.2. Version 2.0.7-release, 26 mar 2013
A.3. Version 2.0.6-release, 22 oct 2012
A.4. Version 2.0.5-release, 28 jul 2012
A.5. Version 2.0.4-release, 02 mar 2012
A.6. Version 2.0.3-release, 23 dec 2011
A.7. Version 2.0.2-beta, 15 nov 2011
A.8. Version 2.0.1-beta, 22 apr 2011
A.9. Version 1.10-beta, 19 jul 2010
A.10. Version 0.9.9-release, 02 dec 2009
A.11. Version 0.9.9-rc2, 08 apr 2009
A.12. Version 0.9.9-rc1, 17 nov 2008
A.13. Version 0.9.8.1, 30 oct 2008
A.14. Version 0.9.8, 14 jul 2008
A.15. Version 0.9.7, 02 apr 2007
A.16. Version 0.9.7-rc2, 15 dec 2006
A.17. Version 0.9.7-rc1, 26 oct 2006
A.18. Version 0.9.6, 24 jul 2006
A.19. Version 0.9.6-rc1, 26 jun 2006

A.1. Version 2.0.8-release, 26 apr 2013
=======================================

Bug fixes
---------

   * fixed #1515, log strings over 2KB were clipped when
     query_log_format=plain
   * fixed #1514, RT index disk chunk lose attribute update on daemon
     restart
   * fixed #1512, crash while formatting log messages
   * fixed #1511, crash on indexing PostgreSQL data source with MVA
     attributes
   * fixed #1509, blend_chars vs incomplete multi-form and overshort
   * fixed #1504, RT binlog replay vs descending tid on update
   * fixed #1499, sql_field_str2wordcount actually is int, not string
   * fixed #1498, now working with exceptions starting with number too
   * fixed #1496, multiple destination keywords in wordform
   * fixed #1494, lost 'mod', '%' operations in select list. Also corrected
     few typers in the doc.
   * fixed #1490, expand_keywords vs prefix
   * fixed #1487, `id` in expression fixed
   * fixed #1483, snippets limits fix
   * fixed #1481, shebang config changes check on rotation
   * fixed #1479, port handling in PHP Sphinx API
   * fixed #1474, daemon crash at SphinxQL packet overflows max_packet_size
   * fixed #1472, crash on loading index to indextool for check
   * fixed #1465, expansion_limit got lost in index rotation
   * fixed #1427, #1506, utf8 3 and 4-bytes codepoints
   * fixed #1405, between with mixed int float values

A.2. Version 2.0.7-release, 26 mar 2013
=======================================

Bug fixes
---------

   * fixed #1475, memory leak in the expression parser
   * fixed #1457, error messages over 2KB were clipped
   * fixed #1454, searchd did not display an error message when the binlog
     path did not exist
   * fixed #1441, SHOW META in a query batch was returning the last
     non-batch error
   * fixed #1435, typo in the documentation
   * fixed #1430, rt_flush_period now works even with a disabled binlog
   * fixed #1427, overlong 4-byte UTF-8 codes in source text could cause
     indexer crashes or index corruption
   * fixed #1418, warnings from local index searches were lost with
     dist_threads>0
   * fixed #1417, crash handler now works on searchd startup stage, too
     (eg. to report index load time crashes)
   * fixed #1410, bad numerics like '123abc' now result in a proper
     SphinxQL error message
   * fixed #1404, a tiny memory leak in shared mutex
   * fixed #1394, race in --iostats caused incorrect I/O statistics in
     threaded modes
   * fixed #1391, QUORUM operator vs docinfo=inline returned wrong
     attribute values
   * fixed #1389, edge case in the ORDER operator caused occasionaly
     searchd crashes
   * fixed #1382, query parts with field limits but without real keywords
     (like '@name {') are now simply ignored and no longer cause a query
     syntax error
   * fixed #1370, Windows indexer builds failed to fetch rows from MSSQL
     2012
   * fixed #1368, ORDER BY RAND() did not work in RT indexes
   * fixed #1364, queries with hitless words could occasionally crash
     searchd
   * fixed #1363, '*' in charset_table was causing query syntax errors with
     enable_star=1
   * fixed #1353, added filtering by 'id' syntax (in addition to '@id') to
     SphinxSE
   * fixed #1346, fixed NEAR operator behavior vs duplicated keywords
   * fixed #1345, invalid PROXIMITY operator threshold now causes a query
     syntax error rather than unexpected search behavior
   * fixed #1343, misconfigured indexes with 0 full text fields are now
     explicitly forbidden
   * fixed #1342, specific error messages (from the preload stage) went
     missing when failing to load the indexes
   * fixed #1339, no warning on inconsistent word statistics
   * fixed #1335, typo in searchd help screen
   * fixed #1334, typo in SELECT documentation
   * fixed #1316, PHRASE operator did not match in a rare self-repeating
     document/query case
   * fixed #1297, letting queries complete gracefully instead of killing
     them off in seamless_rotate=1, workers=prefork case
   * fixed #1295, mentioned index naming requirements (proper identifier)
     in the FROM clause docs
   * fixed #1221, incorrect results when using @groupby in select list via
     SphinxAPI with compat_sphinxql_magics=0
   * fixed #1180, special SPZ chars occasionally leaking into snippets
   * fixed #1171, preforked children did not reload logs on SIGUSR1
   * fixed #1150, added support for `id` syntax in DELETE and parents in
     WHERE
   * fixed #1135, crashes when using MVA/strings attributes in expression
     ranker
   * fixed #1124, corrupted attributes after merging with an empty index
   * fixed #1090, SphinxSE snippets UDF updated to support MySQL 5.5
   * fixed #1041, added initial support for MVA updates (and other mutex
     protected things) on FreeBSD
   * fixed #999, fullscan returned empty result sets in mixed batches of
     fullscan and fulltext queries
   * fixed #921, document count/bytes 32bit overflow in indexer progress
     output
   * fixed #539, added processing suffix rules with dots in .affix file to
     spelldump
   * fixed #481, rotation did not work on Windows with preopen=1
   * fixed #268, added warnings about duplicate elements in xmlpipe2
   * fixed CSphStaticMutex (double initialization issue)
   * fixed documentation typo in SQL data sources
   * fixed too-late initialization of mutex at daemon
   * fixed that an instance of searchd resurrected by watchdog could leak
     resources and/or crash
   * added a console message about crashes during index loading at startup
   * added more debug info about failed index loading

A.3. Version 2.0.6-release, 22 oct 2012
=======================================

Bug fixes
---------

   * fixed #1322, J connector seems to be broken in rel20 , but works in
     trunk
   * fixed #1321, 'set names utf8' passes, but 'set names utf-8' doesn't
     because of syntax error '-'
   * fixed #1318, unhandled float comparison operators at filter
   * fixed #1317, FD leaks on thread seamless rotation
   * fixed #1313, crash on stopping daemon with incorrect RT index config
   * fixed #1306, 'jolly roger ;)', and '(((((((((9 brackets)' crashes
     searchd
   * fixed #1304, OS X debug compilation
   * fixed #1302, daemon random crashes on OS X
   * fixed #1301, indexer fails to send rotate signal
   * fixed #1300, lost index settings on attach
   * fixed #1299, daemon failed to rotate ATTACHed plain index
   * fixed #1289, SENTENCE or PARAGRAPH searching leak memory
   * fixes #1285, crash on running searchd with syslog and watchdog
   * fixed #1279, linking against explicitly disabled iconv. Also added
     --with-libexpat to config options, which sometimes required on systems
     without XML support
   * fixed #1278, broken unixODBC detection in configure script.
   * fixed #1277, broken build on some toolchains (like uClibc) where not
     defined LLONG_MIN, added ULLONG_MAX
   * fixed #1274, large spa ( >4GB ) file hasn't loaded
   * fixed #1269, crash at RT index with MVA from disk chunk previously
     updated
   * fixed #1268, unuseful warning removed
   * fixed #1264, string and MVA attributes aliasing works again
   * fixed #1254, its now possible to add indexes using --rotate
   * fixed #1249, SphinxQL unusable with PHP >= 5.4.5
   * fixed #1246, attributes of 100 character length not being saved
   * fixed #1234, case sensitive GROUP BY attribute
   * fixed #1216, typos, mem_limit default size and RT documentation
   * fixed #1148, RT documentation updated
   * fixed #1140, mem_limit default value
   * fixed #1138, updated documentation on sql_attr_string
   * fixed #1129, snippets vs empty files and empty filenames
   * fixed #1123, configure compatibility fix
   * fixed #1122, 64bit sql_range_step
   * fixed #1082, crashes and deadlocks on OS X with workers=threads and
     field leak of read-write lock
   * fixed #1081, select only count distinct attr1 but group by attr2
   * fixed #1064, mistake while working with timestamp functions
   * fixed #1043, inaccurate distinct count in case many indexes or
     distributed index
   * fixed #1042, arithmetic expressions overflow
   * fixed #1007, Russian stemming on big endian systems
   * fixed #986, asserting in SetRankingMode (PHP API)
   * fixed #975, incorrect ranking in some rare cases
   * fixed #967, Python API type checking error
   * fixed #934, API vs fullscan vs non-empty query
   * fixed #899, error if using SetFilterRange as HAVING from SQL
   * fixed #867, indexer accepts index names starting with digit or _
   * fixed #699, signed vs unsigned 64-bit DocIDs in SphinxQL
   * fixed #668, now ignoring single @ character (incorrect field operator)
   * fixed #611, @! operator vs non-existent field, updated documentation
   * fixed #412, multiple --filter arguments work as they should in search
     utility
   * fixed #108, support for system libstemmer library. The sources of
     libstemmer placed into libstemmer_c is preferred, but the system lib
     will be tried if no sources found
   * fixed ORDER BY output at query log with SphinxQL mode
   * fixed documentation entry about sql_joined_field
   * fixed sample config file
   * fixed x64 configurations for libstemmer

A.4. Version 2.0.5-release, 28 jul 2012
=======================================

Bug fixes
---------

   * fixed #1258, xmlpipe2 refused to index indexes with docinfo=inline
   * fixed #1257, legacy groupby modes vs dist_threads could occasionally
     return wrong search results (race condition)
   * fixed #1253, missing single-word query performance optimization
     (simplified ranker) vs prefix-expanded keywords vs dict=keywords
   * fixed #1252, COUNT(*) vs dist_threads could occasionally crash (race
     condition)
   * fixed #1251, missing expression support in the IN() function
   * fixed #1245, FlushAttributes mistakenly disabled by
     attr_flush_period=0 setting
   * fixed #1244, per-API-command (search, update, etc) statistics were not
     updated by SphinxQL requests
   * fixed #1243, misc issues (broken statistics, weights, checks) with
     very long keywords having blended parts in RT indexes
   * fixed #1240, embedded xmlpipe2 schema with more attributes than the
     sphinx.conf one caused indexer to crash
   * fixed #1239, memory leak when optimizing ABS(const) and other 1-arg
     functions
   * fixed #1228, #761, #1183, #1190, #1198, misc issues occasonally caused
     by MVA updates (crash on SaveAttributes; index rotation vs index name
     and TID; looped MVA updates; persistent MVA removal on rotation)
   * fixed #1227, API queries with SetGeoAnchor() were logged incorrectly
     in SphinxQL-format query logs (query_log_format=sphinxql)
   * fixed #1214, phrase query parsing issues when blend_chars contained
     a quote (") symbol
   * fixed #1213, attribute aliases were not recognized by the subsequent
     SELECT items
   * fixed #1212, indextool failed to check hitless keywords
   * fixed #1210, crash when indexing an index with joined fields only (no
     regular fields)
   * fixed #1209, xmlpipe_fixup_utf8 off by a byte on certain (pretty rare)
     malformed sequences
   * fixed #1202, various issues with CALL KEYWORDS vs RT indexes (crashes
     vs dict=keywords, missing modifiers in output)
   * fixed #1201, snippets vs query_mode=1 vs complex OR-queries could
     occasionally crash
   * fixed #1197, indexer running out of disk space could either crash, or
     fail to display a proper error message
   * fixed #1185, keywords with wildcards were not handled when
     highlighting the entire document
   * fixed #1184, indexer crash when ngram_chars was set, but ngram_len=0
   * fixed #1182, indexer crash on certain combinations of docinfo=inline
     vs bitfields
   * fixed #1181, GROUP BY on a MVA64 was truncated at 32 bits
   * fixed #1179, passage_boundary in snippets could get ignored (when
     highlighting the entire document)
   * fixed #1178, indexer could crash when charset_table specified
     out-of-bounds codes
   * fixed #1177, SPZ queries in snippets erroneously required
     passage_boundary option to be explicitly set
   * fixed #1176, multi-queries with a GROUP/ORDER BY on a string
     attributed crashed
   * fixed #1175, connection id mismatch in SphinxQL-format query logs
   * fixed #1167, nested parentheses in a full-text query could mistakenly
     reset preceding field or zone limit operator
   * fixed #1158, float range filters were not supported in a multi-query
     batch optimizer
   * fixed #1157, broken gcc-4.7 build
   * fixed #1156, empty result set instead of an error message when
     querying distributed indexes with compat_sphinxql_magic=1 and hitting
     an error
   * fixed #1143, dash after a number incorrectly parsed as an operator NOT
   * fixed #1137, searchd --stopwait hanged when the running instance
     crashed during shutdown
   * fixed #1136, high idle CPU load on systems without
     pthread_timed_lock()
   * fixed #1134, issues with prefork workers on systems without
     pthread_timed_lock()
   * fixed #1133, BuildExcerpts() on a distributed index with load_files
     did not distribute the jobs
   * fixed #1126, inaccurate hits sorting progress report on joined field
     indexing
   * fixed #1121, occasional bad entries (wrong characters or invalid SQL)
     in SphinxQL-format query log
   * fixed #1118, libsphinxclient requests failed when using SPH_RANK_EXPR
   * fixed #1073, improved handling of wordforms/multiforms rules referring
     to stopwords
   * fixed #1062, bigint filter ranges truncated when searching via
     SphinxQL
   * fixed #1052, SphinxSE range arguments with leading zeroes mistakenly
     parsed as octal
   * fixed #1011, negative MVA64 values mistakenly converted to positive
     (on indexing and/or output)
   * fixed #974, crash when logging queries over 2048 bytes with
     performance counters enabled
   * fixed #909, field-end modifier was ignored when followed by
     a non-whitespace syntax character (eg quote or bracket)
   * fixed #907, issue with bigint filtering (large positive or negative
     values)
   * fixed #906, #1074, Mac OS X 10.7.3 builds (conflicting memory
     allocation routines in Sphinx and external libs)
   * fixed #901, #1066, sending bigger request packets was broken in Python
     API
   * fixed #879, filters on weight-dependent expressions did not work
     correctly
   * fixed #553, default/missing port value was not handled properly in
     SetServer() API call
   * fixed that blended vs multiforms vs min_word_len could hang the query
     parser
   * fixed missing command-line switches documentation

A.5. Version 2.0.4-release, 02 mar 2012
=======================================

Bug fixes
---------

   * fixed #605, pack vs mysql compress
   * fixed #783, #862, #917, #985, #990, #1032 documentation bugs
   * fixed #885, bitwise AND/OR were not available via API
   * fixed #984, crash on indexing data with MAGIC_CODE_ZONE symbol
   * fixed #1004, RT index loses words from dictionary on segments merging
     with id64 enabled
   * fixed #1035, daemon doesn't properly handle FDs in case of socket
     overflow FD_SETSIZE ( *nix, preopen_indexes=0, worker=threads )
   * fixed #1038, quoted string for API select
   * fixed #1046, head SPZ overflow, snippet generation at non fast with
     SPZ
   * fixed #1048, distributed index can't sort \ filter because of missed
     attributes
   * fixed #1050, expression ranker vs agents
   * fixed #1051, added MVA64 support to UDFs
   * fixed #1054, max_query_time not handled properly on searching at RT
     index
   * fixed #1055, expansion_limit on searching at RT disk chunks
   * fixed #1057, daemon crashes on generating snippet with 0 documents
     provided
   * fixed #1060, load_files_scattered don't work
   * fixed #1065, libsphinxclient vs distribute index (agents)
   * fixed #1067, modifiers were not escaped in legacy query emulation
   * fixed #1071, master - agent communication got slower for a large query
   * fixed #1076, #1077, (redundant copying, and a possible mutex leak with
     uservars)
   * fixed #1078, blended vs FIELD_END
   * fixed #1084 crash \ index corruption on loading persist MVA
   * fixed #1091, RT attach of plain index with string \ MVA attributes
     prior regular attributes
   * fixed #1092, update got binloged with wrong TID
   * fixed #1098, crash on creating large expression
   * fixed #1099, cleaning up temporary files on fail of indexing
   * fixed #1100, missing xmlpipe_attr_bigint config directive
   * fixed #1101, now ignoring dashes within keywords when dash is not in
     charset_table
   * fixed #1103, ZONE operator incorrectly works on more than one keywords
     in a simple zone
   * fixed #1106, optimized WHERE id=value, WHERE id IN (values_list)
     clauses used in SELECT, UPDATE statements
   * fixed #1112, Sphinx doesn't work out-of-the-box because the collision
     of binlog_path option
   * fixed #1116, crash on FLUSH RTINDEX unknown-index-name
   * fixed #1117, occasional RT headers corruption (leading to crashes
     and/or missing results)
   * fixed #1119, missing expression ranker support in SphinxSE
   * fixed #1120, negative total_found, docs and hits counter on huge
     indexes

A.6. Version 2.0.3-release, 23 dec 2011
=======================================

Bug fixes
---------

   * fixed #1031, SphinxQL parsing syntax for MVA at insert \ replace
     statements
   * fixed #1027, stalls on attribute update in high-concurrency load
   * fixed #1026, daemon crash on malformed API command
   * fixed #1021, max_children option has been ignored with worker=threads
   * fixed #1020, crash on large attribute files loading
   * fixed #1014, crash on rotation when index has been removed from config
     file (worker=threads, *nix box)
   * fixed #1001, broken MVA files in RT index while saving disk chunk
   * fixed #995, crash on empty MVA updates
   * fixed #994, crash on daemon shutdown with seamless_rotate=0 and
     workers=threads
   * fixed #993, #998, crash on replay DELETE statement vs RT index with
     dict=keywords, fixed sequential INSERT into dict=keywords index right
     after INSERT into dict=crc index
   * fixed #991, crash on indexing mssql source with mssql_unicode enabled
   * fixed #983, #950, crash on host name lookup (SphinxSE with MySQL 5.5)
   * fixed #981, snippet inconsistency with allow_empty=0
   * fixed #980, broken index produced by index merge in rare cases
   * fixed #971, absent error message at master on agent "maxed out"
   * fixed #695, #815, #835, #866, malformed warnings in SphinxQL
   * fixed build of SphinxSE with MySQL 5.1
   * fixed crash log for 'fork' and 'prefork' workers

A.7. Version 2.0.2-beta, 15 nov 2011
====================================

Major new features
------------------

   * added keywords dictionary (dict=keywords) support to RT indexes
   * added MVA, index_exact_words support to RT indexes (#888)
   * added MVA64 (a set of BIGINTs) support to both disk and RT indexes
     (rt_attr_multi_64 directive)
   * added an expression-based ranker, and a number of new ranking factors
   * added ATTACH INDEX statement that converts a disk index to RT index
   * added WHERE clause support to UPDATE statement
   * added bigint, float, and MVA attribute support to UPDATE statement

New features
------------

   * added support for upto 256 searchable fields (was upto 32 before)
   * added FIBONACCI() function to expressions
   * added load_files_scattered option to snippets
   * added implicit attribute type promotions in multi-index result sets
     (#939)
   * added index names to indexer progress message on merge (#928)
   * added --replay-flags switch to searchd
   * added string attribute support and a few previously missing snippets
     options to SphinxSE
   * added previously missing Status(), SetConnectTimeout() API calls to
     Python API
   * added ORDER BY RAND() support to SELECT statement
   * added Sphinx version to Windows crash log
   * added RT index support to indextool --check (checks disk chunks only)
     (#877)
   * added prefork_rotation_throttle directive (preforked children restart
     delay, in milliseconds) (#873)
   * added on_file_field_error directive (different sql_file_field handling
     modes)
   * added manpages for all the programs
   * added syslog logging support
   * added sentence, paragraph, and zone support in html_strip_mode=retain
     mode to snippets
   * optimized search performance with many ZONE operators
   * improved suggestion tool (added Levenshtein limit, removed extra DB
     fetch)
   * improved sentence extraction (handles salutations, starting initials
     better now)
   * changed max_filter_values sanity check to 10M values

New SphinxQL features
---------------------

   * added FLUSH RTINDEX statement
   * added dist_threads directive (parallel processing), load_files,
     load_files_scattered, batch syntax (multiple documents) support to
     CALL SNIPPETS statement
   * added OPTION comment='...' support to SELECT statement (#944)
   * added SHOW VARIABLES statement
   * added dummy handlers for SET TRANSACTION, SET NAMES, SELECT @@sysvar
     statements, and for sql_auto_is_null, sql_mode, and @@-style variables
     (like @@tx_isolation) in SET statement (better MySQL
     frameworks/connectors support)
   * added complete SphinxQL error logging (all errors are logged now, not
     just SELECTs)
   * improved SELECT statement syntax, made expressions aliases optional

Bug fixes
---------

   * fixed #982, empty binlogs prevented upgraded daemon from starting up
   * fixed #978, libsphinxclient build failed on sparc/sparc64 solaris
   * fixed #977, eliminated (most) compiler warnings
   * fixed #969, broken expression MVA/string argument type check prevented
     IF(IN(mva..)) and other valid expressions from working
   * fixed #966, NOT IN @global_var syntax was not supported
   * fixed #958, mem_limit over INT_MAX was not clamped
   * fixed #954, UTF-8 snippets could crash on malformed data
   * fixed #951, UTF-8 snippets could hang on malformed data
   * fixed #947, bad float column type was reported via SphinxQL, breaking
     some clients
   * fixed #940, group-by with a small enough max_matches limit could
     occasionaly crash and/or sort wrongly
   * fixed #932, sending huge queries to agents occasionally failed (mainly
     on Windows)
   * fixed #926, snippets did not highlight widlcard matches with
     morphology enabled
   * fixed #918, crash logger did not report a proper query in dist_threads
     case
   * fixed #916, watchdog caused (endless) respawns if there was a crash
     during shutdown
   * fixed #904, attribute names were not forcibly case-folded in some API
     calls (eg. SetGroupDistinct)
   * fixed #902, query parser did not support stopword_step=0
   * fixed #897, network sockets dangled (open but unattended) while
     replaying binlog
   * fixed #855, allow_empty option in snippets did not always work
     correctly
   * fixed #854, indexing with many bigint attributes and docinfo=inline
     crashed
   * fixed #838, RT MVA insertion did not sort MVA values, caused matching
     issues
   * fixed #833, duplicate MVA values were not eliminated on update
   * fixed #832, certain (overshort/incorrect) documents crashed indexing
     MS SQL Unicode columns
   * fixed #829, query parser did not properly handle numerics with
     blend_chars
   * fixed #814, group-by string attributes in RT indexes dit not always
     work correctly
   * fixed #812, utf8 stemming produced unexpected stems on words with
     single-byte chars
   * fixed #808, huge queries crashed logging with
     query_log_format=sphinxql
   * fixed #806, stray single-star keyword crashed on querying
   * fixed #798, snippets ignored index_exact_words in query_mode
   * fixed #797, RT klist loader had an occasional off-by-one crash
   * fixed #791, preopen_indexes erroneously defaulted to 0 on Windows
   * fixed #790, huge dictionaries (over 4 GB) did not work
   * fixed #786, inplace_enable could occasionally corrupt the indexes
   * fixed #775, doc had a typo (soundex vs metaphone)
   * fixed #772, snippets duplicated blended chars on a SPZ boundary
   * fixed #762, query parser truncated digit-only keywords over 15 digits
   * fixed #736, query parser dit not properly handle blended/special char
     sequence
   * fixed #726, rotation of an index with a changed attribute count
     crashed
   * fixed #687, querying multiple indexes with index weights and sort-by
     expression produced incorrect (unadjusted) weights
   * fixed #585, (unsupported) string ordinals were silently zeroed out
     with docinfo=inline (instead of failing)
   * fixed #583, certain keywords could occasionally crash multiforms
   * fixed that concurrent MVA updates could crash
   * fixed that query parser did not ignore a pure blended token with
     a leading modifier
   * fixed that query parser did not properly handle a modifier followed by
     a dash
   * fixed that substring indexing with dict=crc did not support
     index_exact_words and zones
   * fixed that in a rare edge case common subtree cache could crash
   * fixed that empty result set returned the full schema (rather than
     SELECT-ed columns)
   * fixed that SphinxQL did not have a sanity check for (currently
     unsupported) result set schemas over 250 attributes
   * fixed that updates on regular indexes were not binlogged
   * fixed that multi-query optimization check for expressions did not
     handle multi-index case
   * fixed that SphinxSE did not build vs MySQL 5.5 release
   * fixed that proximity_bm25 ranker could yield incorrect weight on
     duplicated keywords
   * fixed that prefix expansion with dict=keyword occasionally crashed
   * fixed that strip_path did not work on RT disk chunks
   * fixed that exclude filters were not properly logged in
     query_log_format=sphinxql mode
   * fixed that plain string attribute check in indextool --check was
     broken
   * fixed that Java API did not let specify a connection timeout
   * fixed that ordinal and wordcount attributes could not be fetched via
     SphinxQL
   * fixed that in a rare edge case OR/ORDER would not match properly
   * fixed that sending (huge) query response did not handle EINTR properly
   * fixed that SPH04 ranker could yield incorrectly high weight in some
     cases
   * fixed that C API did not let zero out cutoff, max_matches settings
   * fixed that on a persistent connection there were occasionally issues
     handling signals while doing network reads/waitss
   * fixed that in a rare edge case (field start modifier in a certain
     complex query) querying crashed
   * fixed that snippets did not support dist_threads with load_files=0
   * fixed that in some extremely rare edge cases tiny parts of an index
     could end up corrupted with dict=keywords
   * fixed that field/zone conditions were not propagated to expanded
     keywords with dict=keywords

A.8. Version 2.0.1-beta, 22 apr 2011
====================================

New general features
--------------------

   * added remapping support to blend_chars directive
   * added multi-threaded snippet batches support (requires a batch sent
     via API, dist_threads, and load_files)
   * added collations (collation_server, collation_libc_locale directives)
   * added support for sorting and grouping on string attributes (ORDER BY,
     GROUP BY, WITHING GROUP ORDER BY)
   * added UDF support (plugin_dir directive; CREATE FUNCTION, DROP
     FUNCTION statements)
   * added query_log_format directive, SET GLOBAL query_log_format |
     log_level = ... statements; and connection id tracking
   * added sql_column_buffers directive, fixed out-of-buffer column
     handling in ODBC/MS SQL sources
   * added blend_mode directive that enables indexing multiple variants of
     a blended sequence
   * added UNIX socket support to C, Ruby APIs
   * added ranged query support to sql_joined_field
   * added rt_flush_period directive
   * added thread_stack directive
   * added SENTENCE, PARAGRAPH, ZONE operators (and index_sp, index_zones
     directives)
   * added keywords dictionary support (and dict, expansion_limit
     directives)
   * added passage_boundary, emit_zones options to snippets
   * added a watchdog process in threaded mode
   * added persistent MVA updates
   * added crash dumps to searchd.log, deprecated crash_log_path directive
   * added id32 index support in id64 binaries (EXPERIMENTAL)
   * added SphinxSE support for DELETE and REPLACE on SphinxQL tables

New SphinxQL features
---------------------

   * added new, more SQL compliant SphinxQL syntax; and
     a compat_sphinxql_magics directive
   * added CRC32(), DAY(), MONTH(), YEAR(), YEARMONTH(), YEARMONTHDAY()
     functions
   * added DIV, MOD, and % operators
   * added reverse_scan=(0|1) option to SELECT
   * added support for MySQL packets over 16M
   * added dummy SHOW VARIABLES, SHOW COLLATION, and SET
     character_set_results support (to support handshake with certain
     client libraries and frameworks)
   * added mysql_version_string directive (to workaround picky MySQL client
     libraries)
   * added support for global filter variables, SET GLOBAL
     @uservar=(int_list)
   * added DELETE ... IN (id_list) syntax support
   * added C-style comments syntax (for example, SELECT /*!40000 some
     comment*/ id FROM test)
   * added UPDATE ... WHERE id=X syntax support
   * added SphinxQL multi-query support
   * added DESCRIBE, SHOW TABLES statements

New command-line switches
-------------------------

   * added --print-queries switch to indexer that dumps SQL queries it runs
   * added --sighup-each switch to indexer that rotates indexes one by one
   * added --strip-path switch to searchd that skips file paths embedded in
     the index(-es)
   * added --dumpconfig switch to indextool that dumps an index header in
     sphinx.conf format

Major changes and optimizations
-------------------------------

   * changed default preopen_indexes value to 1
   * optimized English stemmer (results in 1.3x faster snippets and
     indexing with morphology=stem_en)
   * optimized snippets, 1.6x general speedup
   * optimized const-list parsing in SphinxQL
   * optimized full-document highlighting CPU/RAM use
   * optimized binlog replay (improved performance on K-list update)

Bug fixes
---------

   * fixed #767, joined fields vs ODBC sources
   * fixed #757, wordforms shared by indexes with different settings
   * fixed #733, loading of indexes in formats prior to v.14
   * fixed #763, occasional snippets failures
   * fixed #648, occasionally missed rotations on multiple SIGHUPs
   * fixed #750, an RT segment merge leading to false positives and/or
     crashes in some cases
   * fixed #755, zones in snippets output
   * fixed #754, stopwords counting at snippet passage generation
   * fixed #723, fork/prefork index rotation in children processes
   * fixed #696, freeze on zero threshold in quorum operator
   * fixed #732, query escaping in SphinxSE
   * fixed #739, occasional crashes in MT mode on result set send
   * fixed #746, crash with a named list in SphinxQL option
   * fixed #674, AVG vs group order
   * fixed #734, occasional crashes attempting to report NULL errors
   * fixed #829, tail hits within field position modifier
   * fixed #712, missing query_mode, force_all_words snippet option
     defaults in Java API
   * fixed #721, added dupe removal on RT batch INSERT/REPLACE
   * fixed #720, potential extraneous highlighting after a blended keyword
   * fixed #702, exceptions vs star search
   * fixed #666, ext2 query grouping vs exceptions
   * fixed #688, WITHIN GROUP ORDER BY related crash
   * fixed #660, multi-queue batches vs dist_threads
   * fixed #678, crash on dict=keywords vs xmlpipe vs min_prefix_len
   * fixed #596, ECHILD vs scripted configs
   * fixed #653, dependency in expression, sorting, grouping
   * fixed #661, concurrent distributed searches vs workers=threads
   * fixed #646, crash on status query via UNIX socket
   * fixed #589, libexpat.dll missing from some Win32 build types
   * fixed #574, quorum match order
   * fixed multiple documentation issues (#372, #483, #495, #601, #623,
     #632, #654)
   * fixed that ondisk_dict did not affect RT indexes
   * fixed that string attributes check in indextool --check was
     erroneously sensitive to string data order
   * fixed a rare crash when using BEFORE operator
   * fixed an issue with multiforms vs BuildKeywords()
   * fixed an edge case in OR operator (emitted wrong hits order sometimes)
   * fixed aliasing in docinfo accessors that lead to very rare crashes
     and/or missing results
   * fixed a syntax error on a short token at the end of a query
   * fixed id64 filtering and performance degradation with range filters
   * fixed missing rankers in libsphinxclient
   * fixed missing SPH04 ranker in SphinxSE
   * fixed column names in sql_attr_multi sample (works with example.sql
     now)
   * fixed an issue with distributed local+remote setup vs aggregate
     functions
   * fixed case sensitive columns names in RT indexes
   * fixed a crash vs strings from multiple indexes in result set
   * fixed blended keywords vs snippets
   * fixed secure_connection vs MySQL protocol vs MySQL.NET connector
   * fixed that Python API did not works with Python 2.3
   * fixed overshort_step vs snippets
   * fixed keyword staistics vs dist_threads searching
   * fixed multiforms vs query parsing (vs quorum)
   * fixed missed quorum words vs RT segments
   * fixed blended keywords occasionally skipping extra character when
     querying (eg "abc[]")
   * fixed Python API to handle int32 values
   * fixed prefix and infix indexing of joined fields
   * fixed MVA ranged query
   * fixed missing blended state reset on document boundary
   * fixed a crash on missing index while replaying binlog
   * fixed an error message on filter values overrun
   * fixed passage duplication in snippets in weight_order mode
   * fixed select clauses over 1K vs remote agents
   * fixed overshort accounting vs soft-whitespace tokens
   * fixed rotation vs workers=threads
   * fixed schema issues vs distributed indexes
   * fixed blended-escaped sequence parsing issue
   * fixed MySQL IN clause (values order etc)
   * fixed that post_index did not execute when 0 documents were
     succesfully indexed
   * fixed field position limit vs many hits
   * fixed that joined fields missed an end marker at field end
   * fixed that xxx_step settings were missing from .sph index header
   * fixed libsphinxclient missing request cleanup in sphinx_query() (eg
     after network errors)
   * fixed that index_weights were ignored when grouping
   * fixed multi wordforms vs blend_chars
   * fixed broken MVA output in SphinxQL
   * fixed a few RT leaks
   * fixed an issue with RT string storage going missing
   * fixed an issue with repeated queries vs dist_threads
   * fixed an issue with string attributes vs buffer overrun in SphinxQL
   * fixed unexpected character data warnings within ignored xmlpipe tags
   * fixed a crash in snippets with NEAR syntax query
   * fixed passage duplication in snippets
   * fixed libsphinxclient SIGPIPE handling
   * fixed libsphinxclient vs VS2003 compiler bug

A.9. Version 1.10-beta, 19 jul 2010
===================================

   * added RT indexes support (Chapter 4, Real-time indexes)
   * added prefork and threads support (workers directives)
   * added multi-threaded local searches in distributed indexes
     (dist_threads directive)
   * added common subquery cache (subtree_docs_cache, subtree_hits_cache
     directives)
   * added string attributes support (sql_attr_string, sql_field_string,
     xml_attr_string, xml_field_string directives)
   * added indexing-time word counter (sql_attr_str2wordcount,
     sql_field_str2wordcount directives)
   * added CALL SNIPPETS(), CALL KEYWORDS() SphinxQL statements
   * added field_weights, index_weights options to SphinxQL SELECT
     statement
   * added insert-only SphinxQL-talking tables to SphinxSE
     (connection='sphinxql://host[:port]/index')
   * added select option to SphinxSE queries
   * added backtrace on crash to searchd
   * added SQL+FS indexing, aka loading files by names fetched from SQL
     (sql_file_field directive)
   * added a watchdog in threads mode to searchd
   * added automatic row phantoms elimination to index merge
   * added hitless indexing support (hitless_words directive)
   * added --check, --strip-path, --htmlstrip, --dumphitlist ... --wordid
     switches to indextool
   * added --stopwait, --logdebug switches to searchd
   * added --dump-rows, --verbose switches to indexer
   * added "blended" characters indexing support (blend_chars directive)
   * added joined/payload field indexing (sql_joined_field directive)
   * added FlushAttributes() API call
   * added query_mode, force_all_words, limit_passages, limit_words,
     start_passage_id, load_files, html_strip_mode, allow_empty options,
     and %PASSAGE_ID% macro in before_match, after_match options to
     BuildExcerpts() API call
   * added @groupby/@count/@distinct columns support to SELECT (but not to
     expressions)
   * added query-time keyword expansion support (expand_keywords directive,
     SPH_RANK_SPH04 ranker)
   * added query batch size limit option (max_batch_queries directive; was
     hardcoded)
   * added SINT() function to expressions
   * improved SphinxQL syntax error reporting
   * improved expression optimizer (better constant handling)
   * improved dash handling within keywords (no longer treated as an
     operator)
   * improved snippets (better passage selection/trimming, around option
     now a hard limit)
   * optimized index format that yields ~20-30% smaller indexes
   * optimized sorting code (indexing time 1-5% faster on average; 100x
     faster in worst case)
   * optimized searchd startup time (moved .spa preindexing to indexer),
     added a progress bar
   * optimized queries against indexes with many attributes (eliminated
     redundant copying)
   * optimized 1-keyword queries (performace regression introduced in
     0.9.9)
   * optimized SphinxQL protocol overheads, and performance on bigger
     result sets
   * optimized unbuffered attributes writes on index merge
   * changed attribute handling, duplicate names are strictly forbidden now
   * fixed that SphinxQL sessions could stall shutdown
   * fixed consts with leading minus in SphinxQL
   * fixed AND/OR precedence in expressions
   * fixed #334, AVG() on integers was not computed in floats
   * fixed #371, attribute flush vs 2+ GB files
   * fixed #373, segfault on distributed queries vs certain libc versions
   * fixed #398, stopwords not stopped in prefix/infix indexes
   * fixed #404, erroneous MVA failures in indextool --check
   * fixed #408, segfault on certain query batches (regular scan, plus
     a scan with MVA groupby)
   * fixed #431, occasional shutdown hangs in preforked workers
   * fixed #436, trunk checkout builds vs Solaris sh
   * fixed #440, escaping vs parentheses declared as valid in charset_table
   * fixed #442, occasional non-aligned free in MVA indexing
   * fixed #447, occasional crashes in MVA indexing
   * fixed #449, pconn busyloop on aborted clients on certain arches
   * fixed #465, build issue on Alpha
   * fixed #468, build issue in libsphinxclient
   * fixed #472, multiple stopword files failing to load
   * fixed #489, buffer overflow in query logging
   * fixed #493, Python API assertion after error returned from Query()
   * fixed #500, malformed MySQL packet when sending MVAs
   * fixed #504, SIGPIPE in libsphinxclient
   * fixed #506, better MySQL protocol commands support in SphinxQL (PING
     etc)
   * fixed #509, indexing ranged results from stored procedures

A.10. Version 0.9.9-release, 02 dec 2009
========================================

   * added Open, Close, Status calls to libsphinxclient (C API)
   * added automatic persistent connection reopening to PHP, Python APIs
   * added 64-bit value/range filters, fullscan mode support to SphinxSE
   * MAJOR CHANGE, our IANA assigned ports are 9312 and 9306 respectively
     (goodbye, trusty 3312)
   * MAJOR CHANGE, erroneous filters now fail with an error (were silently
     ignored before)
   * optimized unbuffered .spa writes on merge
   * optimized 1-keyword queries ranking in extended2 mode
   * fixed #441 (IO race in case of highly conccurent load on a preopened)
   * fixed #434 (distrubuted indexes were not searchable via MySQL
     protocol)
   * fixed #317 (indexer MVA progress counter)
   * fixed #398 (stopwords not removed from search query)
   * fixed #328 (broken cutoff)
   * fixed #250 (now quoting paths w/spaces when installing Windows
     service)
   * fixed #348 (K-list was not updated on merge)
   * fixed #357 (destination index were not K-list-filtered on merge)
   * fixed #369 (precaching .spi files over 2 GBs)
   * fixed #438 (missing boundary proximity matches)
   * fixed #371 (.spa flush in case of files over 2 GBs)
   * fixed #373 (crashes on distributed queries via mysql proto)
   * fixed critical bugs in hit merging code
   * fixed #424 (ordinals could be misplaced during indexing in case of
     bitfields etc)
   * fixed #426 (failing SE build on Solaris; thanks to Ben Beecher)
   * fixed #423 (typo in SE caused crash on SHOW STATUS)
   * fixed #363 (handling of read_timeout over 2147 seconds)
   * fixed #376 (minor error message mismatch)
   * fixed #413 (minus in SphinxQL)
   * fixed #417 (floats w/o leading digit in SphinxQL)
   * fixed #403 (typo in SetFieldWeights name in Java API)
   * fixed index rotation vs persistent connections
   * fixed backslash handling in SphinxQL parser
   * fixed uint unpacking vs. PHP 5.2.9 (possibly other versions)
   * fixed #325 (filter settings send from SphinxSE)
   * fixed #352 (removed mysql wrapper around close() in SphinxSE)
   * fixed #389 (display error messages through SphinxSE status variable)
   * fixed linking with port-installed iconv on OS X
   * fixed negative 64-bit unpacking in PHP API
   * fixed #349 (escaping backslash in query emulation mode)
   * fixed #320 (disabled multi-query route when select items differ)
   * fixed #353 (better quorum counts check)
   * fixed #341 (merging of trailing hits; maybe other ranking issues too)
   * fixed #368 (partially; @field "" caused crashes; now resets field
     limit)
   * fixed #365 (field mask was leaking on field-limited terms)
   * fixed #339 (updated debug query dumper)
   * fixed #361 (added SetConnectTimeout() to Java API)
   * fixed #338 (added missing fullscan to mode check in Java API)
   * fixed #323 (added floats support to SphinxQL)
   * fixed #340 (support listen=port:proto syntax too)
   * fixed #332 (\r is legal SphinxQL space now)
   * fixed xmlpipe2 K-lists
   * fixed #322 (safety gaps in mysql protocol row buffer)
   * fixed #313 (return keyword stats for empty indexes too)
   * fixed #344 (invalid checkpoints after merge)
   * fixed #326 (missing CLOCK_xxx on FreeBSD)

A.11. Version 0.9.9-rc2, 08 apr 2009
====================================

   * added IsConnectError(), Open(), Close() calls to Java API (bug #240)
   * added read_buffer, read_unhinted directives
   * added checks for build options returned by mysql_config (builds on
     Solaris now)
   * added fixed-RAM index merge (bug #169)
   * added logging chained queries count in case of (optimized)
     multi-queries
   * added GEODIST() function
   * added --status switch to searchd
   * added MySpell (OpenOffice) affix file support (bug #281)
   * added ODBC support (both Windows and UnixODBC)
   * added support for @id in IN() (bug #292)
   * added support for aggregate functions in GROUP BY (namely AVG, MAX,
     MIN, SUM)
   * added MySQL UDF that builds snippets using searchd
   * added write_buffer directive (defaults to 1M)
   * added xmlpipe_fixup_utf8 directive
   * added suggestions sample
   * added microsecond precision int64 timer (bug #282)
   * added listen_backlog directive
   * added max_xmlpipe2_field directive
   * added initial SphinxQL support to mysql41 handler, SELECT .../SHOW
     WARNINGS/STATUS/META are handled
   * added support for different network protocols, and mysql41 protocol
   * added fieldmask ranker, updated SphinxSE list of rankers
   * added mysql_ssl_xxx directives
   * added --cpustats (requires clock_gettime()) and --status switches to
     searchd
   * added performance counters, Status() API call
   * added overshort_step and stopword_step directives
   * added strict order operator (aka operator before, eg. "one << two <<
     three")
   * added indextool utility, moved --dumpheader there, added
     --debugdocids, --dumphitlist options
   * added own RNG, reseeded on @random sort query (bug #183)
   * added field-start and field-end modifiers support (syntax is "^hello
     world$"; field-end requires reindex)
   * added MVA attribute support to IN() function
   * added AND, OR, and NOT support to expressions
   * improved logging of (optimized) multi-queries (now logging chained
     query count)
   * improved handshake error handling, fixed protocol version byte order
     (omg)
   * updated SphinxSE to protocol 1.22
   * allowed phrase_boundary_step=-1 (trick to emulate keyword expansion)
   * removed SPH_MAX_QUERY_WORDS limit
   * fixed CLI search vs documents missing from DB (bug #257)
   * fixed libsphinxclient results leak on subsequent sphinx_run_queries
     call (bug #256)
   * fixed libsphinxclient handling of zero max_matches and cutoff (bug
     #208)
   * fixed Java API over-64K string reads (eg. big snippets) in Java API
     (bug #181)
   * fixed Java API 2nd Query() after network error in 1st Query() call
     (bug #308)
   * fixed typo-class bugs in SetFilterFloatRange (bug #259), SetSortMode
     (bug #248)
   * fixed missing @@relaxed support (bug #276), fixed missing error on
     @nosuchfield queries, documented @@relaxed
   * fixed UNIX socket permissions to 0777 (bug #288)
   * fixed xmlpipe2 crash on schemas with no fields, added better document
     structure checks
   * fixed (and optimized) expr parser vs IN() with huge (10K+) args count
   * fixed double EarlyCalc() in fullscan mode (minor performance impact)
   * fixed phrase boundary handling in some cases (on buffer end, on
     trailing whitespace)
   * fixes in snippets (aka excerpts) generation
   * fixed inline attrs vs id64 index corruption
   * fixed head searchd crash on config re-parse failure
   * fixed handling of numeric keywords with leading zeroes such as "007"
     (bug #251)
   * fixed junk in SphinxSE status variables (bug #304)
   * fixed wordlist checkpoints serialization (bug #236)
   * fixed unaligned docinfo id access (bug #230)
   * fixed GetRawBytes() vs oversized blocks (headers with over 32K
     charset_table should now work, bug #300)
   * fixed buffer overflow caused by too long dest wordform, updated tests
   * fixed IF() return type (was always int, is deduced now)
   * fixed legacy queries vs. special chars vs. multiple indexes
   * fixed write-write-read socket access pattern vs Nagle vs delays vs
     FreeBSD (oh wow)
   * fixed exceptions vs query-parser issue
   * fixed late calc vs @weight in expressions (bug #285)
   * fixed early lookup/calc vs filters (bug #284)
   * fixed emulated MATCH_ANY queries (empty proximity and phrase queries
     are allowed now)
   * fixed MATCH_ANY ranker vs fields with no matches
   * fixed index file size vs inplace_enable (bug #245)
   * fixed that old logs were not closed on USR1 (bug #221)
   * fixed handling of '!' alias to NOT operator (bug #237)
   * fixed error handling vs query steps (step failure was not reported)
   * fixed querying vs inline attributes
   * fixed stupid bug in escaping code, fixed EscapeString() and made it
     static
   * fixed parser vs @field -keyword, foo|@field bar, "" queries (bug #310)

A.12. Version 0.9.9-rc1, 17 nov 2008
====================================

   * added min_stemming_len directive
   * added IsConnectError() API call (helps distingusih API vs remote
     errors)
   * added duplicate log messages filter to searchd
   * added --nodetach debugging switch to searchd
   * added blackhole agents support for debugging/testing (agent_blackhole
     directive)
   * added max_filters, max_filter_values directives (were hardcoded
     before)
   * added int64 expression evaluation path, automatic inference, and
     BIGINT() enforcer function
   * added crash handler for debugging (crash_log_path directive)
   * added MS SQL (aka SQL Server) source support (Windows only,
     mssql_winauth and mssql_unicode directives)
   * added indexer-side column unpacking feature (unpack_zlib,
     unpack_mysqlcompress directives)
   * added nested brackers and NOTs support to query language, rewritten
     query parser
   * added persistent connections support (Open() and Close() API calls)
   * added index_exact_words feature, and exact form operator to query
     language ("hello =world")
   * added status variables support to SphinxSE (SHOW STATUS LIKE
     'sphinx_%')
   * added max_packet_size directive (was hardcoded at 8M before)
   * added UNIX socket support, and multi-interface support (listen
     directive)
   * added star-syntax support to BuildExcerpts() API call
   * added inplace inversion of .spa and .spp (inplace_enable directive,
     1.5-2x less disk space for indexing)
   * added builtin Czech stemmer (morphology=stem_cz)
   * added IDIV(), NOW(), INTERVAL(), IN() functions to expressions
   * added index-level early-reject based on filters
   * added MVA updates feature (mva_updates_pool directive)
   * added select-list feature with computed expressions support (see
     SetSelect() API call, test.php --select switch), protocol 1.22
   * added integer expressions support (2x faster than float)
   * added multiforms support (multiple source words in wordforms file)
   * added legacy rankers (MATCH_ALL/MATCH_ANY/etc), removed legacy
     matching code (everything runs on V2 engine now)
   * added field position limit modifier to field operator (syntax:
     @title[50] hello world)
   * added killlist support (sql_query_killlist directive,
     --merge-killlists switch)
   * added on-disk SPI support (ondisk_dict directive)
   * added indexer IO stats
   * added periodic .spa flush (attr_flush_period directive)
   * added config reload on SIGHUP
   * added per-query attribute overrides feature (see SetOverride() API
     call); protocol 1.21
   * added signed 64bit attrs support (sql_attr_bigint directive)
   * improved HTML stripper to also skip PIs (<? ... ?>, such as <?php ...
     ?>)
   * improved excerpts speed (upto 50x faster on big documents)
   * fixed a short window of searchd inaccessibility on startup (started
     listen()ing too early before)
   * fixed .spa loading on systems where read() is 2GB capped
   * fixed infixes vs morphology issues
   * fixed backslash escaping, added backslash to EscapeString()
   * fixed handling of over-2GB dictionary files (.spi)

A.13. Version 0.9.8.1, 30 oct 2008
==================================

   * added configure script to libsphinxclient
   * changed proximity/quorum operator syntax to require whitespace after
     length
   * fixed potential head process crash on SIGPIPE during "maxed out"
     message
   * fixed handling of incomplete remote replies (caused over-degraded
     distributed results, in rare cases)
   * fixed sending of big remote requests (caused distributed requests to
     fail, in rare cases)
   * fixed FD_SET() overflow (caused searchd to crash on startup, in rare
     cases)
   * fixed MVA vs distributed indexes (caused loss of 1st MVA value in
     result set)
   * fixed tokenizing of exceptions terminated by specials (eg. "GPS AT&T"
     in extended mode)
   * fixed buffer overrun in stemmer on overlong tokens occasionally
     emitted by proximity/quorum operator parser (caused crashes on certain
     proximity/quorum queries)
   * fixed wordcount ranker (could be dropping hits)
   * fixed --merge feature (numerous different fixes, caused broken
     indexes)
   * fixed --merge-dst-range performance
   * fixed prefix/infix generation for stopwords
   * fixed ignore_chars vs specials
   * fixed misplaced F_SETLKW check (caused certain build types, eg. RPM
     build on FC8, to fail)
   * fixed dictionary-defined charsets support in spelldump, added \x-style
     wordchars support
   * fixed Java API to properly send long strings (over 64K; eg. long
     document bodies for excerpts)
   * fixed Python API to accept offset/limit of 'long' type
   * fixed default ID range (that filtered out all 64-bit values) in Java
     and Python APIs

A.14. Version 0.9.8, 14 jul 2008
================================

Indexing
--------

   * added support for 64-bit document and keyword IDs, --enable-id64
     switch to configure
   * added support for floating point attributes
   * added support for bitfields in attributes, sql_attr_bool directive and
     bit-widths part in sql_attr_uint directive
   * added support for multi-valued attributes (MVA)
   * added metaphone preprocessor
   * added libstemmer library support, provides stemmers for a number of
     additional languages
   * added xmlpipe2 source type, that supports arbitrary fields and
     attributes
   * added word form dictionaries, wordforms directive (and spelldump
     utility)
   * added tokenizing exceptions, exceptions directive
   * added an option to fully remove element contents to HTML stripper,
     html_remove_elements directive
   * added HTML entities decoder (with full XHTML1 set support) to HTML
     stripper
   * added per-index HTML stripping settings, html_strip, html_index_attrs,
     and html_remove_elements directives
   * added IO load throttling, max_iops and max_iosize directives
   * added SQL load throttling, sql_ranged_throttle directive
   * added an option to index prefixes/infixes for given fields only,
     prefix_fields and infix_fields directives
   * added an option to ignore certain characters (instead of just treating
     them as whitespace), ignore_chars directive
   * added an option to increment word position on phrase boundary
     characters, phrase_boundary and phrase_boundary_step directives
   * added --merge-dst-range switch (and filters) to index merging feature
     (--merge switch)
   * added mysql_connect_flags directive (eg. to reduce indexing time MySQL
     network traffic and/or time)
   * improved ordinals sorting; now runs in fixed RAM
   * improved handling of documents with zero/NULL ids, now skipping them
     instead of aborting

Search daemon
-------------

   * added an option to unlink old index on succesful rotation, unlink_old
     directive
   * added an option to keep index files open at all times (fixes subtle
     races on rotation), preopen and preopen_indexes directives
   * added an option to profile searchd disk I/O, --iostats command-line
     option
   * added an option to rotate index seamlessly (fully avoids query
     stalls), seamless_rotate directive
   * added HTML stripping support to excerpts (uses per-index settings)
   * added 'exact_phrase', 'single_passage', 'use_boundaries',
     'weight_order 'options to BuildExcerpts() API call
   * added distributed attribute updates propagation
   * added distributed retries on master node side
   * added log reopen on SIGUSR1
   * added --stop switch (sends SIGTERM to running instance)
   * added Windows service mode, and --servicename switch
   * added Windows --rotate support
   * improved log timestamping, now with millisecond precision

Querying
--------

   * added extended engine V2 (faster, cleaner, better; SPH_MATCH_EXTENDED2
     mode)
   * added ranking modes support (V2 engine only; SetRankingMode() API
     call)
   * added quorum searching support to query language (V2 engine only;
     example: "any three of all these words"/3)
   * added query escaping support to query language, and EscapeString() API
     call
   * added multi-field syntax support to query language (example:
     "@(field1,field2) something"), and @@relaxed field checks option
   * added optional star-syntax ('word*') support in keywords, enable_star
     directive (for prefix/infix indexes only)
   * added full-scan support (query must be fully empty; can perform
     block-reject optimization)
   * added COUNT(DISTINCT(attr)) calculation support, SetGroupDistinct()
     API call
   * added group-by on MVA support, SetArrayResult() PHP API call
   * added per-index weights feature, SetIndexWeights() API call
   * added geodistance support, SetGeoAnchor() API call
   * added result set sorting by arbitrary expressions in run time (eg.
     "@weight+log(price)*2.5"), SPH_SORT_EXPR mode
   * added result set sorting by @custom compile-time sorting function (see
     src/sphinxcustomsort.inl)
   * added result set sorting by @random value
   * added result set merging for indexes with different schemas
   * added query comments support (3rd arg to Query()/AddQuery() API calls,
     copied verbatim to query log)
   * added keyword extraction support, BuildKeywords() API call
   * added binding field weights by name, SetFieldWeights() API call
   * added optional limit on query time, SetMaxQueryTime() API call
   * added optional limit on found matches count (4rd arg to SetLimits()
     API call, so-called 'cutoff')

APIs and SphinxSE
-----------------

   * added pure C API (libsphinxclient)
   * added Ruby API (thanks to Dmytro Shteflyuk)
   * added Java API
   * added SphinxSE support for MVAs (use varchar), floats (use float),
     64bit docids (use bigint)
   * added SphinxSE options "floatrange", "geoanchor", "fieldweights",
     "indexweights", "maxquerytime", "comment", "host" and "port"; and
     support for "expr:CLAUSE"
   * improved SphinxSE max query size (using MySQL condition pushdown),
     upto 256K now

General
-------

   * added scripting (shebang syntax) support to config files (example:
     #!/usr/bin/php in the first line)
   * added unified config handling and validation to all programs
   * added unified documentation
   * added .spec file for RPM builds
   * added automated testing suite
   * improved index locking, now fcntl()-based instead of buggy
     file-existence-based
   * fixed unaligned RAM accesses, now works on SPARC and ARM

Changes and fixes since 0.9.8-rc2
---------------------------------

   * added pure C API (libsphinxclient)
   * added Ruby API
   * added SetConnectTimeout() PHP API call
   * added allowed type check to UpdateAttributes() handler (bug #174)
   * added defensive MVA checks on index preload (protection against broken
     indexes, bug #168)
   * added sphinx-min.conf sample file
   * added --without-iconv switch to configure
   * removed redundant -lz dependency in searchd
   * removed erroneous "xmlpipe2 deprecated" warning
   * fixed EINTR handling in piped read (bug #166)
   * fixup query time before logging and sending to client (bug #153)
   * fixed attribute updates vs full-scan early-reject index (bug #149)
   * fixed gcc warnings (bug #160)
   * fixed mysql connection attempt vs pgsql source type (bug #165)
   * fixed 32-bit wraparound when preloading over 2 GB files
   * fixed "out of memory" message vs over 2 GB allocs (bug #116)
   * fixed unaligned RAM access detection on ARM (where unaligned reads do
     not crash but produce wrong results)
   * fixed missing full scan results in some cases
   * fixed several bugs in --merge, --merge-dst-range
   * fixed @geodist vs MultiQuery and filters, @expr vs MultiQuery
   * fixed GetTokenEnd() vs 1-grams (was causing crash in excerpts)
   * fixed sql_query_range to handle empty strings in addition to NULL
     strings (Postgres specific)
   * fixed morphology=none vs infixes
   * fixed case sensitive attributes names in UpdateAttributes()
   * fixed ext2 ranking vs. stopwords (now using atompos from query parser)
   * fixed EscapeString() call
   * fixed escaped specials (now handled as whitespace if not in charset)
   * fixed schema minimizer (now handles type/size mismatches)
   * fixed word stats in extended2; stemmed form is now returned
   * fixed spelldump case folding vs dictionary-defined character sets
   * fixed Postgres BOOLEAN handling
   * fixed enforced "inline" docinfo on empty indexes (normally ok, but
     index merge was really confused)
   * fixed rare count(distinct) out-of-bounds issue (it occasionaly caused
     too high @distinct values)
   * fixed hangups on documents with id=DOCID_MAX in some cases
   * fixed rare crash in tokenizer (prefixed synonym vs. input stream eof)
   * fixed query parser vs "aaa (bbb ccc)|ddd" queries
   * fixed BuildExcerpts() request in Java API
   * fixed Postgres specific memory leak
   * fixed handling of overshort keywords (less than min_word_len)
   * fixed HTML stripper (now emits space after indexed attributes)
   * fixed 32-field case in query parser
   * fixed rare count(distinct) vs. querying multiple local indexes vs.
     reusable sorter issue
   * fixed sorting of negative floats in SPH_SORT_EXTENDED mode

A.15. Version 0.9.7, 02 apr 2007
================================

   * added support for sql_str2ordinal_column
   * added support for upto 5 sort-by attrs (in extended sorting mode)
   * added support for separate groups sorting clause (in group-by mode)
   * added support for on-the-fly attribute updates (PRE-ALPHA; will change
     heavily; use for preliminary testing ONLY)
   * added support for zero/NULL attributes
   * added support for 0.9.7 features to SphinxSE
   * added support for n-grams (alpha, 1-grams only for now)
   * added support for warnings reported to client
   * added support for exclude-filters
   * added support for prefix and infix indexing (see max_prefix_len,
     max_infix_len)
   * added @* syntax to reset current field to query language
   * added removal of duplicate entries in query index order
   * added PHP API workarounds for PHP signed/unsigned braindamage
   * added locks to avoid two concurrent indexers working on same index
   * added check for existing attributes vs. docinfo=none case
   * improved groupby code a lot (better precision, and upto 25x times
     faster in extreme cases)
   * improved error handling and reporting
   * improved handling of broken indexes (reports error instead of
     hanging/crashing)
   * improved mmap() limits for attributes and wordlists (now able to map
     over 4 GB on x64 and over 2 GB on x32 where possible)
   * improved malloc() pressure in head daemon (search time should not
     degrade with time any more)
   * improved test.php command line options
   * improved error reporting (distributed query, broken index etc issues
     now reported to client)
   * changed default network packet size to be 8M, added extra checks
   * fixed division by zero in BM25 on 1-document collections (in extended
     matching mode)
   * fixed .spl files getting unlinked
   * fixed crash in schema compatibility test
   * fixed UTF-8 Russian stemmer
   * fixed requested matches count when querying distributed agents
   * fixed signed vs. unsigned issues everywhere (ranged queries, CLI
     search output, and obtaining docid)
   * fixed potential crashes vs. negative query offsets
   * fixed 0-match docs vs. extended mode vs. stats
   * fixed group/timestamp filters being ignored if querying from older
     clients
   * fixed docs to mention pgsql source type
   * fixed issues with explicit '&' in extended matching mode
   * fixed wrong assertion in SBCS encoder
   * fixed crashes with no-attribute indexes after rotate

A.16. Version 0.9.7-rc2, 15 dec 2006
====================================

   * added support for extended matching mode (query language)
   * added support for extended sorting mode (sorting clauses)
   * added support for SBCS excerpts
   * added mmap()ing for attributes and wordlist (improves search time,
     speeds up fork() greatly)
   * fixed attribute name handling to be case insensitive
   * fixed default compiler options to simplify post-mortem debugging
     (added -g, removed -fomit-frame-pointer)
   * fixed rare memory leak
   * fixed "hello hello" queries in "match phrase" mode
   * fixed issue with excerpts, texts and overlong queries
   * fixed logging multiple index name (no longer tokenized)
   * fixed trailing stopword not flushed from tokenizer
   * fixed boolean evaluation
   * fixed pidfile being wrongly unlink()ed on bind() failure
   * fixed --with-mysql-includes/libs (they conflicted with well-known
     paths)
   * fixes for 64-bit platforms

A.17. Version 0.9.7-rc1, 26 oct 2006
====================================

   * added alpha index merging code
   * added an option to decrease max_matches per-query
   * added an option to specify IP address for searchd to listen on
   * added support for unlimited amount of configured sources and indexes
   * added support for group-by queries
   * added support for /2 range modifier in charset_table
   * added support for arbitrary amount of document attributes
   * added logging filter count and index name
   * added --with-debug option to configure to compile in debug mode
   * added -DNDEBUG when compiling in default mode
   * improved search time (added doclist size hints, in-memory wordlist
     cache, and used VLB coding everywhere)
   * improved (refactored) SQL driver code (adding new drivers should be
     very easy now)
   * improved exceprts generation
   * fixed issue with empty sources and ranged queries
   * fixed querying purely remote distributed indexes
   * fixed suffix length check in English stemmer in some cases
   * fixed UTF-8 decoder for codes over U+20000 (for CJK)
   * fixed UTF-8 encoder for 3-byte sequences (for CJK)
   * fixed overshort (less than min_word_len) words prepended to next field
   * fixed source connection order (indexer does not connect to all sources
     at once now)
   * fixed line numbering in config parser
   * fixed some issues with index rotation

A.18. Version 0.9.6, 24 jul 2006
================================

   * added support for empty indexes
   * added support for multiple sql_query_pre/post/post_index
   * fixed timestamp ranges filter in "match any" mode
   * fixed configure issues with --without-mysql and --with-pgsql options
   * fixed building on Solaris 9

A.19. Version 0.9.6-rc1, 26 jun 2006
====================================

   * added boolean queries support (experimental, beta version)
   * added simple file-based query cache (experimental, beta version)
   * added storage engine for MySQL 5.0 and 5.1 (experimental, beta
     version)
   * added GNU style configure script
   * added new searchd protocol (all binary, and should be backwards
     compatible)
   * added distributed searching support to searchd
   * added PostgreSQL driver
   * added excerpts generation
   * added min_word_len option to index
   * added max_matches option to searchd, removed hardcoded MAX_MATCHES
     limit
   * added initial documentation, and a working example.sql
   * added support for multiple sources per index
   * added soundex support
   * added group ID ranges support
   * added --stdin command-line option to search utility
   * added --noprogress option to indexer
   * added --index option to search
   * fixed UTF-8 decoder (3-byte codepoints did not work)
   * fixed PHP API to handle big result sets faster
   * fixed config parser to handle empty values properly
   * fixed redundant time(NULL) calls in time-segments mode

--eof--
