Class AllGroupHeadsCollector<T>

java.lang.Object
org.apache.lucene.search.SimpleCollector
org.apache.lucene.search.grouping.AllGroupHeadsCollector<T>
All Implemented Interfaces:
Collector, LeafCollector
Direct Known Subclasses:
AllGroupHeadsCollector.ScoringGroupHeadsCollector, AllGroupHeadsCollector.SortingGroupHeadsCollector

public abstract class AllGroupHeadsCollector<T> extends SimpleCollector
This collector specializes in collecting the most relevant document (group head) for each group that matches the query.

Clients should create new collectors by calling newCollector(GroupSelector, Sort)

  • Field Details

  • Constructor Details

    • AllGroupHeadsCollector

      private AllGroupHeadsCollector(GroupSelector<T> selector, Sort sort)
  • Method Details

    • newCollector

      public static <T> AllGroupHeadsCollector<T> newCollector(GroupSelector<T> selector, Sort sort)
      Create a new AllGroupHeadsCollector based on the type of within-group Sort required
      Type Parameters:
      T - the group value type
      Parameters:
      selector - a GroupSelector to define the groups
      sort - the within-group sort to use to choose the group head document
    • retrieveGroupHeads

      public FixedBitSet retrieveGroupHeads(int maxDoc)
      Parameters:
      maxDoc - The maxDoc of the top level IndexReader.
      Returns:
      a FixedBitSet containing all group heads.
    • retrieveGroupHeads

      public int[] retrieveGroupHeads()
      Returns:
      an int array containing all group heads. The size of the array is equal to number of collected unique groups.
    • groupHeadsSize

      public int groupHeadsSize()
      Returns:
      the number of group heads found for a query.
    • getCollectedGroupHeads

      protected Collection<? extends AllGroupHeadsCollector.GroupHead<T>> getCollectedGroupHeads()
      Returns the collected group heads. Subsequent calls should return the same group heads.
      Returns:
      the collected group heads
    • 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
    • scoreMode

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

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

      protected abstract AllGroupHeadsCollector.GroupHead<T> newGroupHead(int doc, T value, LeafReaderContext context, Scorable scorer) throws IOException
      Create a new GroupHead for the given group value, initialized with a doc, context and scorer
      Throws:
      IOException