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 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(Query childQuery, Filter parentsFilter, ToParentBlockJoinQuery.ScoreMode scoreMode) Create a ToParentBlockJoinQuery.

Method Summary

Methods

Modifier and Type	Method and Description
Object	clone() Returns a clone of this query.
Weight	createWeight(Searcher searcher) Expert: Constructs an appropriate Weight implementation for this query.
boolean	equals(Object _other)
void	extractTerms(Set<Term> terms) Expert: adds all terms occurring in this query to the terms set.
int	hashCode()
Query	rewrite(IndexReader reader) Expert: called to re-write queries into primitive queries.
String	toString(String field) Prints a query to a string, with field assumed to be the default field and omitted.

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(Query childQuery,
                      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 Weight createWeight(Searcher searcher)
                    throws IOException

Description copied from class: Query

Expert: Constructs an appropriate Weight implementation for this query.

Only implemented by primitive queries, which re-write to themselves.

Overrides:

createWeight in class Query

Throws:

IOException

extractTerms

public void extractTerms(Set<Term> terms)

Description copied from class: Query

Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten form.

Overrides:

extractTerms in class Query

rewrite

public Query rewrite(IndexReader reader)
              throws IOException

Description copied from class: Query

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

Overrides:

rewrite in class Query

Throws:

IOException

toString

public String toString(String field)

Description copied from class: Query

Prints a query to a string, with field assumed to be the default field and omitted.

The representation used is one that is supposed to be readable by QueryParser. However, there are the following limitations:

• If the query was created by the parser, the printed representation may not be exactly what was parsed. For example, characters that need to be escaped will be represented without the required backslash.
• Some of the more complicated queries (e.g. span queries) don't have a representation that can be parsed by QueryParser.

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

clone

public Object clone()

Description copied from class: Query

Returns a clone of this query.

Overrides:

clone in class Query