org.apache.lucene.search.join

Class ToParentBlockJoinQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.join.ToParentBlockJoinQuery

All Implemented Interfaces:

Cloneable

public class ToParentBlockJoinQuery
extends Query

This query requires that you index children and parent docs as a single block, using the IndexWriter.addDocuments() or IndexWriter.updateDocuments() API. In each block, the child documents must appear first, ending with the parent document. At search time you provide a Filter identifying the parents, however this Filter must provide an BitSet per sub-reader.

Once the block index is built, use this query to wrap any sub-query matching only child docs and join matches in that child document space up to the parent document space. You can then use this Query as a clause with other queries in the parent document space.

See ToChildBlockJoinQuery if you need to join in the reverse order.

The child documents must be orthogonal to the parent documents: the wrapped child query must never return a parent document.

If you'd like to retrieve TopGroups for the resulting query, use the ToParentBlockJoinCollector. Note that this is not necessary, ie, if you simply want to collect the parent documents and don't need to see which child documents matched under that parent, then you can use any collector.

NOTE: If the overall query contains parent-only matches, for example you OR a parent-only query with a joined child-only query, then the resulting collected documents will be correct, however the TopGroups you get from ToParentBlockJoinCollector will not contain every child for parents that had matched.

See org.apache.lucene.search.join for an overview.

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

Constructor Summary

Constructors

Constructor and Description
ToParentBlockJoinQuery(Query childQuery, BitSetProducer parentsFilter, ScoreMode scoreMode) Create a ToParentBlockJoinQuery.

Method Summary

Methods

Modifier and Type	Method and Description
Weight	createWeight(IndexSearcher searcher, boolean needsScores)
boolean	equals(Object _other)
Query	getChildQuery() Return our child query.
int	hashCode()
Query	rewrite(IndexReader reader)
String	toString(String field)

Methods inherited from class org.apache.lucene.search.Query

clone, getBoost, setBoost, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ToParentBlockJoinQuery

public ToParentBlockJoinQuery(Query childQuery,
                      BitSetProducer parentsFilter,
                      ScoreMode scoreMode)

Create a ToParentBlockJoinQuery.

Parameters:

childQuery - Query matching child documents.

parentsFilter - Filter identifying the parent documents.

scoreMode - How to aggregate multiple child scores into a single parent score.

Method Detail

createWeight

public Weight createWeight(IndexSearcher searcher,
                  boolean needsScores)
                    throws IOException

Overrides:

createWeight in class Query

Throws:

IOException

getChildQuery

public Query getChildQuery()

Return our child query.

rewrite

public Query rewrite(IndexReader reader)
              throws IOException

Overrides:

rewrite in class Query

Throws:

IOException

toString

public String toString(String field)

Specified by:

toString in class Query

equals

public boolean equals(Object _other)

Overrides:

equals in class Query

hashCode

public int hashCode()

Overrides:

hashCode in class Query