Class BlockGroupingCollector

    • Constructor Detail

      • BlockGroupingCollector

        public BlockGroupingCollector​(Sort groupSort,
                                      int topNGroups,
                                      boolean needsScores,
                                      Filter lastDocPerGroup)
                               throws IOException
        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, boolean)
        lastDocPerGroup - a Filter that marks the last document in each group.
        Throws:
        IOException
    • Method Detail

      • getTopGroups

        public TopGroups getTopGroups​(Sort withinGroupSort,
                                      int groupOffset,
                                      int withinGroupOffset,
                                      int maxDocsPerGroup,
                                      boolean fillSortFields)
                               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 FieldCache, etc.)

        Parameters:
        withinGroupSort - The Sort used to sort documents within each group. Passing null is allowed, to sort by relevance.
        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.
        fillSortFields - If true then the Comparable values for the sort fields will be set
        Throws:
        IOException
      • collect

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

        Note: This is called in an inner search loop. For good search performance, implementations of this method should not call Searcher.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 class Collector
        Throws:
        IOException
      • acceptsDocsOutOfOrder

        public boolean acceptsDocsOutOfOrder()
        Description copied from class: Collector
        Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to Collector.collect(int).

        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 true here.

        Specified by:
        acceptsDocsOutOfOrder in class Collector