Class ValueSourceScorer


  • public abstract class ValueSourceScorer
    extends Scorer
    Scorer which returns the result of FunctionValues.floatVal(int) as the score for a document, and which filters out documents that don't match matches(int). This Scorer has a TwoPhaseIterator. This is similar to FunctionQuery, with an added filter.

    Note: If the scores are needed, then the underlying value will probably be fetched/computed twice -- once to filter and next to return the score. If that's non-trivial then consider wrapping it in an implementation that will cache the current value.

    See Also:
    FunctionQuery
    • Method Detail

      • matches

        public abstract boolean matches​(int doc)
                                 throws java.io.IOException
        Override to decide if this document matches. It's called by TwoPhaseIterator.matches().
        Throws:
        java.io.IOException
      • iterator

        public DocIdSetIterator iterator()
        Description copied from class: Scorer
        Return a DocIdSetIterator over matching documents.

        The returned iterator will either be positioned on -1 if no documents have been scored yet, DocIdSetIterator.NO_MORE_DOCS if all documents have been scored already, or the last document id that has been scored otherwise.

        The returned iterator is a view: calling this method several times will return iterators that have the same state.

        Specified by:
        iterator in class Scorer
      • twoPhaseIterator

        public TwoPhaseIterator twoPhaseIterator()
        Description copied from class: Scorer
        Optional method: Return a TwoPhaseIterator view of this Scorer. A return value of null indicates that two-phase iteration is not supported.

        Note that the returned TwoPhaseIterator's approximation must advance synchronously with the Scorer.iterator(): advancing the approximation must advance the iterator and vice-versa.

        Implementing this method is typically useful on Scorers that have a high per-document overhead in order to confirm matches.

        The default implementation returns null.

        Overrides:
        twoPhaseIterator in class Scorer
      • docID

        public int docID()
        Description copied from class: Scorable
        Returns the doc ID that is currently being scored.
        Specified by:
        docID in class Scorable
      • score

        public float score()
                    throws java.io.IOException
        Description copied from class: Scorable
        Returns the score of the current document matching the query.
        Specified by:
        score in class Scorable
        Throws:
        java.io.IOException
      • getMaxScore

        public float getMaxScore​(int upTo)
                          throws java.io.IOException
        Description copied from class: Scorer
        Return the maximum score that documents between the last target that this iterator was shallow-advanced to included and upTo included.
        Specified by:
        getMaxScore in class Scorer
        Throws:
        java.io.IOException
      • matchCost

        protected float matchCost()
        Cost evaluation function which defines the cost of access for the TwoPhaseIterator for this class This method should be overridden for specifying custom cost methods. Used by TwoPhaseIterator.matchCost() for the instance owned by this class
        Returns:
        cost of access