Class BlockGroupingCollector
- java.lang.Object
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- org.apache.lucene.search.SimpleCollector
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- org.apache.lucene.search.grouping.BlockGroupingCollector
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- All Implemented Interfaces:
Collector
,LeafCollector
public class BlockGroupingCollector extends SimpleCollector
BlockGroupingCollector performs grouping with a single pass collector, as long as you are grouping by a doc block field, ie all documents sharing a given group value were indexed as a doc block using the atomicIndexWriter.addDocuments()
orIndexWriter.updateDocuments()
API.This results in faster performance (~25% faster QPS) than the two-pass grouping collectors, with the tradeoff being that the documents in each group must always be indexed as a block. This collector also fills in TopGroups.totalGroupCount without requiring the separate
AllGroupsCollector
. However, this collector does not fill in the groupValue of each group; this field will always be null.NOTE: this collector makes no effort to verify the docs were in fact indexed as a block, so it's up to you to ensure this was the case.
See
org.apache.lucene.search.grouping
for more details including a full code example.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Constructor Summary
Constructors Constructor Description BlockGroupingCollector(Sort groupSort, int topNGroups, boolean needsScores, Weight lastDocPerGroup)
Create the single pass collector.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
collect(int doc)
protected void
doSetNextReader(LeafReaderContext readerContext)
void
finish()
TopGroups<?>
getTopGroups(Sort withinGroupSort, int groupOffset, int withinGroupOffset, int maxDocsPerGroup)
Returns the grouped results.ScoreMode
scoreMode()
void
setScorer(Scorable scorer)
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Methods inherited from class org.apache.lucene.search.SimpleCollector
getLeafCollector
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.lucene.search.LeafCollector
collect, competitiveIterator
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Constructor Detail
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BlockGroupingCollector
public BlockGroupingCollector(Sort groupSort, int topNGroups, boolean needsScores, Weight lastDocPerGroup)
Create the single pass collector.- Parameters:
groupSort
- TheSort
used to sort the groups. The top sorted document within each group according to groupSort, determines how that group sorts against other groups. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.topNGroups
- How many top groups to keep.needsScores
- true if the collected documents require scores, either because relevance is included in the withinGroupSort or because you plan to pass true for either getSscores or getMaxScores togetTopGroups(org.apache.lucene.search.Sort, int, int, int)
lastDocPerGroup
- aWeight
that marks the last document in each group.
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Method Detail
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getTopGroups
public TopGroups<?> getTopGroups(Sort withinGroupSort, int groupOffset, int withinGroupOffset, int maxDocsPerGroup) throws IOException
Returns the grouped results. Returns null if the number of groups collected is <= groupOffset.NOTE: This collector is unable to compute the groupValue per group so it will always be null. This is normally not a problem, as you can obtain the value just like you obtain other values for each matching document (eg, via stored fields, via DocValues, etc.)
- Parameters:
withinGroupSort
- TheSort
used to sort documents within each group.groupOffset
- Which group to start fromwithinGroupOffset
- Which document to start from within each groupmaxDocsPerGroup
- How many top documents to keep within each group.- Throws:
IOException
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setScorer
public void setScorer(Scorable scorer) throws IOException
- Specified by:
setScorer
in interfaceLeafCollector
- Overrides:
setScorer
in classSimpleCollector
- Throws:
IOException
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collect
public void collect(int doc) throws IOException
- Specified by:
collect
in interfaceLeafCollector
- Specified by:
collect
in classSimpleCollector
- Throws:
IOException
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doSetNextReader
protected void doSetNextReader(LeafReaderContext readerContext) throws IOException
- Overrides:
doSetNextReader
in classSimpleCollector
- Throws:
IOException
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finish
public void finish() throws IOException
- Throws:
IOException
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scoreMode
public ScoreMode scoreMode()
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