Class Sequel::Schema::AlterTableGenerator
In: lib/sequel/database/schema_generator.rb
Parent: Object

Schema::AlterTableGenerator is an internal class that the user is not expected to instantiate directly. Instances are created by Database#alter_table. It is used to specify table alteration parameters. It takes a Database object and a block of operations to perform on the table, and gives the Database an array of table altering operations, which the database uses to alter a table‘s description.

For more information on Sequel‘s support for schema modification, see the "Migrations and Schema Modification" guide.

Methods

Attributes

operations  [R]  An array of DDL operations to perform

Public Class methods

Set the Database object to which to apply the DDL, and evaluate the block in the context of this object.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 280
280:       def initialize(db, &block)
281:         @db = db
282:         @operations = []
283:         instance_eval(&block) if block
284:       end

Public Instance methods

Add a column with the given name, type, and opts to the DDL for the table. See CreateTableGenerator#column for the available options.

  add_column(:name, String) # ADD COLUMN name varchar(255)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 290
290:       def add_column(name, type, opts = {})
291:         @operations << {:op => :add_column, :name => name, :type => type}.merge(opts)
292:       end

Add a constraint with the given name and args to the DDL for the table. See CreateTableGenerator#constraint.

  add_constraint(:valid_name, :name.like('A%'))
  # ADD CONSTRAINT valid_name CHECK (name LIKE 'A%')

[Source]

     # File lib/sequel/database/schema_generator.rb, line 299
299:       def add_constraint(name, *args, &block)
300:         @operations << {:op => :add_constraint, :name => name, :type => :check, :check => block || args}
301:       end

Add a foreign key with the given name and referencing the given table to the DDL for the table. See CreateTableGenerator#column for the available options.

You can also pass an array of column names for creating composite foreign keys. In this case, it will assume the columns exist and will only add the constraint. You can provide a :name option to name the constraint.

NOTE: If you need to add a foreign key constraint to a single existing column use the composite key syntax even if it is only one column.

  add_foreign_key(:artist_id, :table) # ADD COLUMN artist_id integer REFERENCES table
  add_foreign_key([:name], :table) # ADD FOREIGN KEY (name) REFERENCES table

PostgreSQL specific options:

:not_valid :Set to true to add the constraint with the NOT VALID syntax. This makes it so that future inserts must respect referential integrity, but allows the constraint to be added even if existing column values reference rows that do not exist. After all the existing data has been cleaned up, validate_constraint can be used to mark the constraint as valid. Note that this option only makes sense when using an array of columns.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 333
333:       def add_foreign_key(name, table, opts = {})
334:         return add_composite_foreign_key(name, table, opts) if name.is_a?(Array)
335:         add_column(name, Integer, {:table=>table}.merge(opts))
336:       end

Add a full text index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 340
340:       def add_full_text_index(columns, opts = {})
341:         add_index(columns, {:type=>:full_text}.merge(opts))
342:       end

Add an index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

  add_index(:artist_id) # CREATE INDEX table_artist_id_index ON table (artist_id)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 348
348:       def add_index(columns, opts = {})
349:         @operations << {:op => :add_index, :columns => Array(columns)}.merge(opts)
350:       end

Add a primary key to the DDL for the table. See CreateTableGenerator#column for the available options. Like add_foreign_key, if you specify the column name as an array, it just creates a constraint:

  add_primary_key(:id) # ADD COLUMN id serial PRIMARY KEY
  add_primary_key([:artist_id, :name]) # ADD PRIMARY KEY (artist_id, name)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 358
358:       def add_primary_key(name, opts = {})
359:         return add_composite_primary_key(name, opts) if name.is_a?(Array)
360:         opts = @db.serial_primary_key_options.merge(opts)
361:         add_column(name, opts.delete(:type), opts)
362:       end

Add a spatial index on the given columns to the DDL for the table. See CreateTableGenerator#index for available options.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 366
366:       def add_spatial_index(columns, opts = {})
367:         add_index(columns, {:type=>:spatial}.merge(opts))
368:       end

Add a unique constraint to the given column(s)

  add_unique_constraint(:name) # ADD UNIQUE (name)
  add_unique_constraint(:name, :name=>:unique_name) # ADD CONSTRAINT unique_name UNIQUE (name)

[Source]

     # File lib/sequel/database/schema_generator.rb, line 307
307:       def add_unique_constraint(columns, opts = {})
308:         @operations << {:op => :add_constraint, :type => :unique, :columns => Array(columns)}.merge(opts)
309:       end

Remove a column from the DDL for the table.

  drop_column(:artist_id) # DROP COLUMN artist_id
  drop_column(:artist_id, :cascade=>true) # DROP COLUMN artist_id CASCADE

[Source]

     # File lib/sequel/database/schema_generator.rb, line 374
374:       def drop_column(name, opts={})
375:         @operations << {:op => :drop_column, :name => name}.merge(opts)
376:       end

Remove a constraint from the DDL for the table. MySQL/SQLite specific options:

:type :Set the type of constraint to drop, either :primary_key, :foreign_key, or :unique.
  drop_constraint(:unique_name) # DROP CONSTRAINT unique_name
  drop_constraint(:unique_name, :cascade=>true) # DROP CONSTRAINT unique_name CASCADE

[Source]

     # File lib/sequel/database/schema_generator.rb, line 385
385:       def drop_constraint(name, opts={})
386:         @operations << {:op => :drop_constraint, :name => name}.merge(opts)
387:       end

Remove an index from the DDL for the table. General options:

:name :The name of the index to drop. If not given, uses the same name that would be used by add_index with the same columns.

PostgreSQL specific options:

:cascade :Cascade the index drop to dependent objects.
:concurrently :Drop the index using CONCURRENTLY, which doesn‘t block operations on the table. Supported in PostgreSQL 9.2+.
:if_exists :Only drop the index if it already exists.
  drop_index(:artist_id) # DROP INDEX table_artist_id_index
  drop_index([:a, :b]) # DROP INDEX table_a_b_index
  drop_index([:a, :b], :name=>:foo) # DROP INDEX foo

[Source]

     # File lib/sequel/database/schema_generator.rb, line 404
404:       def drop_index(columns, options={})
405:         @operations << {:op => :drop_index, :columns => Array(columns)}.merge(options)
406:       end

Modify a column‘s name in the DDL for the table.

  rename_column(:name, :artist_name) # RENAME COLUMN name TO artist_name

[Source]

     # File lib/sequel/database/schema_generator.rb, line 411
411:       def rename_column(name, new_name, opts = {})
412:         @operations << {:op => :rename_column, :name => name, :new_name => new_name}.merge(opts)
413:       end

Modify a column‘s NOT NULL constraint.

  set_column_allow_null(:artist_name, false) # ALTER COLUMN artist_name SET NOT NULL

[Source]

     # File lib/sequel/database/schema_generator.rb, line 436
436:       def set_column_allow_null(name, allow_null)
437:         @operations << {:op => :set_column_null, :name => name, :null => allow_null}
438:       end

Modify a column‘s default value in the DDL for the table.

  set_column_default(:artist_name, 'a') # ALTER COLUMN artist_name SET DEFAULT 'a'

[Source]

     # File lib/sequel/database/schema_generator.rb, line 418
418:       def set_column_default(name, default)
419:         @operations << {:op => :set_column_default, :name => name, :default => default}
420:       end

Modify a column‘s type in the DDL for the table.

  set_column_type(:artist_name, 'char(10)') # ALTER COLUMN artist_name TYPE char(10)

PostgreSQL specific options:

:using :Add a USING clause that specifies how to convert existing values to new values.

[Source]

     # File lib/sequel/database/schema_generator.rb, line 429
429:       def set_column_type(name, type, opts={})
430:         @operations << {:op => :set_column_type, :name => name, :type => type}.merge(opts)
431:       end

[Validate]