Package org.apache.lucene.search.grouping

Class 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 Detail

      • 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

      • reversed

        private final int[] reversed

      • compIDXEnd

        private final int compIDXEnd

      • bottomSlot

        private int bottomSlot

      • queueFull

        private boolean queueFull

      • topGroupDoc

        private int topGroupDoc

      • totalHitCount

        private int totalHitCount

      • totalGroupCount

        private int totalGroupCount

      • docBase

        private int docBase

      • groupEndDocID

        private int groupEndDocID

      • groupCompetes

        private boolean groupCompetes

    • Constructor Detail

      • 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 Detail

      • processGroup

        private void processGroup()
                   throws java.io.IOException
        Throws:
        java.io.IOException

      • getTopGroups

        public TopGroups<?> getTopGroups​(Sort withinGroupSort,
                                 int groupOffset,
                                 int withinGroupOffset,
                                 int maxDocsPerGroup)
                          throws java.io.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:
        java.io.IOException

      • collect

        public void collect​(int doc)
             throws java.io.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 IndexSearcher.doc(int) or IndexReader.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:
        java.io.IOException

      • scoreMode

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