## org.apache.lucene.search.join
Class JoinUtil

    java.lang.Object
      org.apache.lucene.search.join.JoinUtil

    public final class JoinUtil

extends Object

Utility for query time joining using `TermsQuery` and `TermsCollector`.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Method Summary
`static org.apache.lucene.search.Query` `createJoinQuery(String fromField, String toField, org.apache.lucene.search.Query fromQuery, org.apache.lucene.search.IndexSearcher fromSearcher)` Method for query time joining.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

### createJoinQuery

    public static org.apache.lucene.search.Query createJoinQuery(String fromField,
                                                                 String toField,
                                                                 org.apache.lucene.search.Query fromQuery,
                                                                 org.apache.lucene.search.IndexSearcher fromSearcher)
                                                          throws IOException

  Method for query time joining.

  Execute the returned query with a `IndexSearcher` to retrieve all documents that have the same terms in the to field that match with documents matching the specified fromQuery and have the same terms in the from field. Notice: Can't join documents with a fromField that holds more then one term.

  Parameters:
    `fromField` - The from field to join from
    `toField` - The to field to join to
    `fromQuery` - The query to match documents on the from side
    `fromSearcher` - The searcher that executed the specified fromQuery
  Returns:
    a `Query` instance that can be used to join documents based on the terms in the from and to field
  Throws:
    `IOException` - If I/O related errors occur