Module org.apache.lucene.grouping
Package org.apache.lucene.search.grouping

Class BlockGroupingCollector

java.lang.Object
org.apache.lucene.search.SimpleCollector
org.apache.lucene.search.grouping.BlockGroupingCollector
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 atomic 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.

  • Field Details

    • pendingSubDocs

      private int[] pendingSubDocs

    • pendingSubScores

      private float[] pendingSubScores

    • subDocUpto

      private int subDocUpto

    • groupSort

      private final Sort groupSort

    • topNGroups

      private final int topNGroups

    • lastDocPerGroup

      private final Weight lastDocPerGroup

    • needsScores

      private final boolean needsScores

    • comparators

      private final FieldComparator<?>[] comparators

    • leafComparators

      private final LeafFieldComparator[] leafComparators

    • reversed

      private final int[] reversed

    • compIDXEnd

      private final int compIDXEnd

    • bottomSlot

      private int bottomSlot

    • queueFull

      private boolean queueFull

    • currentReaderContext

      private LeafReaderContext currentReaderContext

    • topGroupDoc

      private int topGroupDoc

    • totalHitCount

      private int totalHitCount

    • totalGroupCount

      private int totalGroupCount

    • docBase

      private int docBase

    • groupEndDocID

      private int groupEndDocID

    • lastDocPerGroupBits

      private DocIdSetIterator lastDocPerGroupBits

    • scorer

      private Scorable scorer

    • groupQueue

      private final BlockGroupingCollector.GroupQueue groupQueue

    • groupCompetes

      private boolean groupCompetes

  • Constructor Details

    • BlockGroupingCollector

      public BlockGroupingCollector(Sort groupSort, int topNGroups, boolean needsScores, Weight lastDocPerGroup)
      Create the single pass collector.
      Parameters:
      groupSort - The Sort 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 to getTopGroups(org.apache.lucene.search.Sort, int, int, int)
      lastDocPerGroup - a Weight that marks the last document in each group.

  • Method Details

    • processGroup

      private void processGroup() throws IOException
      Throws:
      IOException

    • 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 - The Sort used to sort documents within each group.
      groupOffset - Which group to start from
      withinGroupOffset - Which document to start from within each group
      maxDocsPerGroup - How many top documents to keep within each group.
      Throws:
      IOException

    • setScorer

      public void setScorer(Scorable scorer) throws IOException
      Description copied from interface: LeafCollector
      Called before successive calls to LeafCollector.collect(int). Implementations that need the score of the current document (passed-in to LeafCollector.collect(int)), should save the passed-in Scorer and call scorer.score() when needed.
      Specified by:
      setScorer in interface LeafCollector
      Overrides:
      setScorer in class SimpleCollector
      Throws:
      IOException

    • collect

      public void collect(int doc) throws IOException
      Description copied from interface: LeafCollector
      Called once for every document matching a query, with the unbased document number.

      Note: The collection of the current segment can be terminated by throwing a CollectionTerminatedException. In this case, the last docs of the current LeafReaderContext will be skipped and IndexSearcher will swallow the exception and continue collection with the next leaf.

      Note: This is called in an inner search loop. For good search performance, implementations of this method should not call StoredFields.document(int) on every hit. Doing so can slow searches by an order of magnitude or more.

      Specified by:
      collect in interface LeafCollector
      Specified by:
      collect in class SimpleCollector
      Throws:
      IOException

    • doSetNextReader

      protected void doSetNextReader(LeafReaderContext readerContext) throws IOException
      Description copied from class: SimpleCollector
      This method is called before collecting context.
      Overrides:
      doSetNextReader in class SimpleCollector
      Throws:
      IOException

    • finish

      public void finish() throws IOException
      Description copied from interface: LeafCollector
      Hook that gets called once the leaf that is associated with this collector has finished collecting successfully, including when a CollectionTerminatedException is thrown. This is typically useful to compile data that has been collected on this leaf, e.g. to convert facet counts on leaf ordinals to facet counts on global ordinals. The default implementation does nothing.

      Note: It can be assumed that this method will only be called once per LeafCollector instance.

      Throws:
      IOException

    • scoreMode

      public ScoreMode scoreMode()
      Description copied from interface: Collector
      Indicates what features are required from the scorer.