Class ToParentBlockJoinCollector
- java.lang.Object
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- org.apache.lucene.search.Collector
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- org.apache.lucene.search.join.ToParentBlockJoinCollector
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public class ToParentBlockJoinCollector extends org.apache.lucene.search.Collector
Collects parent document hits for a Query containing one more more BlockJoinQuery clauses, sorted by the specified parent Sort. Note that this cannot perform arbitrary joins; rather, it requires that all joined documents are indexed as a doc block (usingIndexWriter.addDocuments(java.util.Collection<org.apache.lucene.document.Document>)
orIndexWriter.updateDocuments(org.apache.lucene.index.Term, java.util.Collection<org.apache.lucene.document.Document>)
). Ie, the join is computed at index time.The parent Sort must only use fields from the parent documents; sorting by field in the child documents is not supported.
You should only use this collector if one or more of the clauses in the query is a
ToParentBlockJoinQuery
. This collector will find those query clauses and record the matching child documents for the top scoring parent documents.Multiple joins (star join) and nested joins and a mix of the two are allowed, as long as in all cases the documents corresponding to a single row of each joined parent table were indexed as a doc block.
For the simple star join you can retrieve the
TopGroups
instance containing eachToParentBlockJoinQuery
's matching child documents for the top parent groups, usinggetTopGroups(org.apache.lucene.search.join.ToParentBlockJoinQuery, org.apache.lucene.search.Sort, int, int, int, boolean)
. Ie, a single query, which will contain two or moreToParentBlockJoinQuery
's as clauses representing the star join, can then retrieve two or moreTopGroups
instances.For nested joins, the query will run correctly (ie, match the right parent and child documents), however, because TopGroups is currently unable to support nesting (each group is not able to hold another TopGroups), you are only able to retrieve the TopGroups of the first join. The TopGroups of the nested joins will not be correct. See
org.apache.lucene.search.join
for a code sample.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Constructor Summary
Constructors Constructor Description ToParentBlockJoinCollector(org.apache.lucene.search.Sort sort, int numParentHits, boolean trackScores, boolean trackMaxScore)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
acceptsDocsOutOfOrder()
void
collect(int parentDoc)
org.apache.lucene.search.grouping.TopGroups<Integer>
getTopGroups(ToParentBlockJoinQuery query, org.apache.lucene.search.Sort withinGroupSort, int offset, int maxDocsPerGroup, int withinGroupOffset, boolean fillSortFields)
Return the TopGroups for the specified BlockJoinQuery.void
setNextReader(org.apache.lucene.index.IndexReader reader, int docBase)
void
setScorer(org.apache.lucene.search.Scorer scorer)
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Constructor Detail
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ToParentBlockJoinCollector
public ToParentBlockJoinCollector(org.apache.lucene.search.Sort sort, int numParentHits, boolean trackScores, boolean trackMaxScore) throws IOException
- Throws:
IOException
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Method Detail
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collect
public void collect(int parentDoc) throws IOException
- Specified by:
collect
in classorg.apache.lucene.search.Collector
- Throws:
IOException
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setNextReader
public void setNextReader(org.apache.lucene.index.IndexReader reader, int docBase) throws IOException
- Specified by:
setNextReader
in classorg.apache.lucene.search.Collector
- Throws:
IOException
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acceptsDocsOutOfOrder
public boolean acceptsDocsOutOfOrder()
- Specified by:
acceptsDocsOutOfOrder
in classorg.apache.lucene.search.Collector
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setScorer
public void setScorer(org.apache.lucene.search.Scorer scorer)
- Specified by:
setScorer
in classorg.apache.lucene.search.Collector
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getTopGroups
public org.apache.lucene.search.grouping.TopGroups<Integer> getTopGroups(ToParentBlockJoinQuery query, org.apache.lucene.search.Sort withinGroupSort, int offset, int maxDocsPerGroup, int withinGroupOffset, boolean fillSortFields) throws IOException
Return the TopGroups for the specified BlockJoinQuery. The groupValue of each GroupDocs will be the parent docID for that group. Note that theGroupDocs.totalHits
, which would be the total number of child documents matching that parent, is not computed (will always be 0). Returns null if no groups matched.- Throws:
IOException
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