public class ToParentBlockJoinCollector extends Collector
IndexWriter.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
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 each
matching child documents for the top parent groups,
getTopGroups(org.apache.lucene.search.join.ToParentBlockJoinQuery, org.apache.lucene.search.Sort, int, int, int, boolean). Ie,
a single query, which will contain two or more
ToParentBlockJoinQuery's as clauses representing the star join,
can then retrieve two or more
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
org.apache.lucene.search.join for a code
|Constructor and Description|
|Modifier and Type||Method and Description|
Called once for every document matching a query, with the unbased document number.
Return the TopGroups for the specified BlockJoinQuery.
Called before collecting from each IndexReader.
Called before successive calls to
public void collect(int parentDoc) throws IOException
Note: This is called in an inner search loop. For good search performance,
implementations of this method should not call
IndexReader.document(int) on every hit.
Doing so can slow searches by an order of magnitude or more.
public void setNextReader(IndexReader reader, int docBase) throws IOException
Collector.collect(int)will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in
public boolean acceptsDocsOutOfOrder()
trueif this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to
Most Lucene Query implementations will visit
matching docIDs in order. However, some queries
(currently limited to certain cases of
BooleanQuery) can achieve faster searching if the
Collector allows them to deliver the
docIDs out of order.
Many collectors don't mind getting docIDs out of
order, so it's important to return
public void setScorer(Scorer scorer)
Collector.collect(int). Implementations that need the score of the current document (passed-in to
Collector.collect(int)), should save the passed-in Scorer and call scorer.score() when needed.
public TopGroups<Integer> getTopGroups(ToParentBlockJoinQuery query, Sort withinGroupSort, int offset, int maxDocsPerGroup, int withinGroupOffset, boolean fillSortFields) throws IOException
GroupDocs.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.