Class BlockGroupingCollector
- All Implemented Interfaces:
Collector,LeafCollector
IndexWriter.addDocuments() or IndexWriter.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
ConstructorsConstructorDescriptionBlockGroupingCollector(Sort groupSort, int topNGroups, boolean needsScores, Weight lastDocPerGroup) Create the single pass collector. -
Method Summary
Modifier and TypeMethodDescriptionvoidcollect(int doc) protected voiddoSetNextReader(LeafReaderContext readerContext) voidfinish()TopGroups<?> getTopGroups(Sort withinGroupSort, int groupOffset, int withinGroupOffset, int maxDocsPerGroup) Returns the grouped results.voidMethods inherited from class org.apache.lucene.search.SimpleCollector
getLeafCollectorMethods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitMethods inherited from interface org.apache.lucene.search.LeafCollector
collect, competitiveIterator
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Constructor Details
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BlockGroupingCollector
public BlockGroupingCollector(Sort groupSort, int topNGroups, boolean needsScores, Weight lastDocPerGroup) Create the single pass collector.- Parameters:
groupSort- TheSortused 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- aWeightthat marks the last document in each group.
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Method Details
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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- TheSortused 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
- Specified by:
setScorerin interfaceLeafCollector- Overrides:
setScorerin classSimpleCollector- Throws:
IOException
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collect
- Specified by:
collectin interfaceLeafCollector- Specified by:
collectin classSimpleCollector- Throws:
IOException
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doSetNextReader
- Overrides:
doSetNextReaderin classSimpleCollector- Throws:
IOException
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finish
- Throws:
IOException
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scoreMode
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