org.apache.lucene.search.join

Class ToParentBlockJoinQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.join.ToParentBlockJoinQuery

All Implemented Interfaces:

Serializable, Cloneable

public class ToParentBlockJoinQuery
extends org.apache.lucene.search.Query

This query requires that you index children and parent docs as a single block, using the IndexWriter.addDocuments(java.util.Collection<org.apache.lucene.document.Document>) or IndexWriter.updateDocuments(org.apache.lucene.index.Term, java.util.Collection<org.apache.lucene.document.Document>) 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 FixedBitSet per sub-reader.

WARNING: to create the parents filter, always use RawTermFilter (so that the filter includes deleted docs), wrapped with CachingWrapperFilter (so that the returned bit set per reader is a FixedBitSet), specifying DeletesMode.IGNORE (so that on reopen, the filter still includes deleted docs). Failure to do this can result in completely wrong documents being returned! For example:

   Filter parents = new CachingWrapperFilter(
                          new RawTermFilter(new Term("parent", "yes")),
                          CachingWrapperFilter.DeletesMode.IGNORE);
 

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.

See Also:

Serialized Form

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ToParentBlockJoinQuery.ScoreMode How to aggregate multiple child hit scores into a single parent score.

Constructor Summary

Constructors

Constructor and Description
ToParentBlockJoinQuery(org.apache.lucene.search.Query childQuery, org.apache.lucene.search.Filter parentsFilter, ToParentBlockJoinQuery.ScoreMode scoreMode) Create a ToParentBlockJoinQuery.

Method Summary

Methods

Modifier and Type	Method and Description
Object	clone()
org.apache.lucene.search.Weight	createWeight(org.apache.lucene.search.Searcher searcher)
boolean	equals(Object _other)
void	extractTerms(Set<org.apache.lucene.index.Term> terms)
int	hashCode()
org.apache.lucene.search.Query	rewrite(org.apache.lucene.index.IndexReader reader)
String	toString(String field)

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

combine, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight

Methods inherited from class java.lang.Object

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

Constructor Detail

ToParentBlockJoinQuery

public ToParentBlockJoinQuery(org.apache.lucene.search.Query childQuery,
                      org.apache.lucene.search.Filter parentsFilter,
                      ToParentBlockJoinQuery.ScoreMode scoreMode)

Create a ToParentBlockJoinQuery.

Parameters:

childQuery - Query matching child documents.

parentsFilter - Filter (must produce FixedBitSet per-seegment) identifying the parent documents.

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

Method Detail

createWeight

public org.apache.lucene.search.Weight createWeight(org.apache.lucene.search.Searcher searcher)
                                             throws IOException

Overrides:

createWeight in class org.apache.lucene.search.Query

Throws:

IOException

extractTerms

public void extractTerms(Set<org.apache.lucene.index.Term> terms)

Overrides:

extractTerms in class org.apache.lucene.search.Query

rewrite

public org.apache.lucene.search.Query rewrite(org.apache.lucene.index.IndexReader reader)
                                       throws IOException

Overrides:

rewrite in class org.apache.lucene.search.Query

Throws:

IOException

toString

public String toString(String field)

Specified by:

toString in class org.apache.lucene.search.Query

equals

public boolean equals(Object _other)

Overrides:

equals in class org.apache.lucene.search.Query

hashCode

public int hashCode()

Overrides:

hashCode in class org.apache.lucene.search.Query

clone

public Object clone()

Overrides:

clone in class org.apache.lucene.search.Query