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

        public boolean score​(Collector collector,
                     int max,
                     int firstDocID)
              throws java.io.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.
        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:
        java.io.IOException

      • nextDoc

        public int nextDoc()
            throws java.io.IOException
        Description copied from class: DocIdSetIterator
        Advances to the next document in the set and returns the doc it is currently on, or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the set.
        NOTE: after the iterator has exhausted you should not call this method, as it may result in unpredicted behavior.
        Specified by:
        nextDoc in class DocIdSetIterator
        Throws:
        java.io.IOException

      • score

        public void score​(Collector collector)
           throws java.io.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:
        java.io.IOException

      • advance

        public int advance​(int target)
            throws java.io.IOException
        Description copied from class: DocIdSetIterator
        Advances to the first beyond the current whose document number is greater than or equal to target, and returns the document number itself. Exhausts the iterator and returns DocIdSetIterator.NO_MORE_DOCS if target is greater than the highest document number in the set.

        The behavior of this method is undefined when called with target ≤ current, or after the iterator has exhausted. Both cases may result in unpredicted behavior.

        When target > current it 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: 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.

        Specified by:
        advance in class DocIdSetIterator
        Throws:
        java.io.IOException

      • cost

        public long cost()
        Description copied from class: DocIdSetIterator
        Returns the estimated cost of this DocIdSetIterator.

        This is generally an upper bound of the number of documents this iterator might match, but may be a rough heuristic, hardcoded value, or otherwise completely inaccurate.

        Specified by:
        cost in class DocIdSetIterator