Package org.apache.lucene.search

Class ScoreCachingWrappingScorer

  • public class ScoreCachingWrappingScorer
extends Scorer
    A Scorer which wraps another scorer and caches the score of the current document. Successive calls to score() will return the same result and will not invoke the wrapped Scorer's score() method, unless the current document has changed.
    This class might be useful due to the changes done to the Collector interface, in which the score is not computed for a document by default, only if the collector requests it. Some collectors may need to use the score in several places, however all they have in hand is a Scorer object, and might end up computing the score of a document more than once.

    • Constructor Detail

      • ScoreCachingWrappingScorer

        public ScoreCachingWrappingScorer​(Scorer scorer)
        Creates a new instance by wrapping the given scorer.

    • Method Detail

      • score

        protected boolean score​(Collector collector,
                        int max,
                        int firstDocID)
                 throws IOException
        Description copied from class: Scorer
        Expert: Collects matching documents in a range. Hook for optimization. Note, firstDocID is added to ensure that DocIdSetIterator.nextDoc() was called before this method.

        NOTE: Because of backwards compatibility, this method is still declared as protected, but it is intended to be public, because it's called from other classes (like BooleanScorer). If you subclass Scorer, you should declare the overridden method as public to ease transition to Lucene 4.0, where it will be public.

        Overrides:
        score in class Scorer
        Parameters:
        collector - The collector to which all matching documents are passed.
        max - Do not score documents past this.
        firstDocID - The first document ID (ensures DocIdSetIterator.nextDoc() is called before this method.
        Returns:
        true if more matching documents may remain.
        Throws:
        IOException

      • getSimilarity

        public Similarity getSimilarity()
        Description copied from class: Scorer
        Returns the Similarity implementation used by this scorer.
        Overrides:
        getSimilarity in class Scorer

      • score

        public void score​(Collector collector)
           throws IOException
        Description copied from class: Scorer
        Scores and collects all matching documents.
        Overrides:
        score in class Scorer
        Parameters:
        collector - The collector to which all matching documents are passed.
        Throws:
        IOException

      • advance

        public int advance​(int target)
            throws IOException
        Description copied from class: DocIdSetIterator
        Advances to the first beyond (see NOTE below) the current whose document number is greater than or equal to target. Returns the current document number or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the set.

        Behaves as if written: 

         int advance(int target) {
   int doc;
   while ((doc = nextDoc()) < target) {
   }
   return doc;
 }
        Some implementations are considerably more efficient than that.

        NOTE: when target ≤ current implementations may opt not to advance beyond their current DocIdSetIterator.docID().

        NOTE: this method may be called with DocIdSetIterator.NO_MORE_DOCS for efficiency by some Scorers. If your implementation cannot efficiently determine that it should exhaust, it is recommended that you check for that value in each call to this method.

        NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.

        Specified by:
        advance in class DocIdSetIterator
        Throws:
        IOException