org.apache.lucene.search.join
Class ToParentBlockJoinQuery

java.lang.Object
  extended by org.apache.lucene.search.Query
      extended by 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 FixedBitSet 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
ToParentBlockJoinQuery(Query childQuery, Filter parentsFilter, ScoreMode scoreMode)
          Create a ToParentBlockJoinQuery.
 
Method Summary
 Weight createWeight(IndexSearcher searcher)
           
 boolean equals(Object _other)
           
 void extractTerms(Set<Term> terms)
           
 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,
                              Filter parentsFilter,
                              ScoreMode scoreMode)
Create a ToParentBlockJoinQuery.

Parameters:
childQuery - Query matching child documents.
parentsFilter - Filter (must produce FixedBitSet per-segment, like FixedBitSetCachingWrapperFilter) identifying the parent documents.
scoreMode - How to aggregate multiple child scores into a single parent score.
Method Detail

createWeight

public Weight createWeight(IndexSearcher searcher)
                    throws IOException
Overrides:
createWeight in class Query
Throws:
IOException

extractTerms

public void extractTerms(Set<Term> terms)
Overrides:
extractTerms in class 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


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