Package org.apache.lucene.queries

Class CustomScoreProvider

java.lang.Object
org.apache.lucene.queries.CustomScoreProvider
public class CustomScoreProvider extends Object
An instance of this subclass should be returned by CustomScoreQuery.getCustomScoreProvider(org.apache.lucene.index.AtomicReaderContext), if you want to modify the custom score calculation of a CustomScoreQuery.

Since Lucene 2.9, queries operate on each segment of an index separately, so the protected context field can be used to resolve doc IDs, as the supplied doc ID is per-segment and without knowledge of the IndexReader you cannot access the document or FieldCache.

Since:
2.9.2

  • Constructor Details

    • CustomScoreProvider

      public CustomScoreProvider(AtomicReaderContext context)
      Creates a new instance of the provider class for the given IndexReader.

  • Method Details

    • customScore

      public float customScore(int doc, float subQueryScore, float[] valSrcScores) throws IOException
      Compute a custom score by the subQuery score and a number of FunctionQuery scores.

      Subclasses can override this method to modify the custom score.

      If your custom scoring is different than the default herein you should override at least one of the two customScore() methods. If the number of function queries is always < 2 it is sufficient to override the other customScore() method, which is simpler.

      The default computation herein is a multiplication of given scores: 

           ModifiedScore = valSrcScore * valSrcScores[0] * valSrcScores[1] * ...
      Parameters:
      doc - id of scored doc.
      subQueryScore - score of that doc by the subQuery.
      valSrcScores - scores of that doc by the FunctionQuery.
      Returns:
      custom score.
      Throws:
      IOException

    • customScore

      public float customScore(int doc, float subQueryScore, float valSrcScore) throws IOException
      Compute a custom score by the subQuery score and the FunctionQuery score.

      Subclasses can override this method to modify the custom score.

      If your custom scoring is different than the default herein you should override at least one of the two customScore() methods. If the number of function queries is always < 2 it is sufficient to override this customScore() method, which is simpler.

      The default computation herein is a multiplication of the two scores: 

           ModifiedScore = subQueryScore * valSrcScore
      Parameters:
      doc - id of scored doc.
      subQueryScore - score of that doc by the subQuery.
      valSrcScore - score of that doc by the FunctionQuery.
      Returns:
      custom score.
      Throws:
      IOException

    • customExplain

      public Explanation customExplain(int doc, Explanation subQueryExpl, Explanation[] valSrcExpls) throws IOException
      Explain the custom score. Whenever overriding customScore(int, float, float[]), this method should also be overridden to provide the correct explanation for the part of the custom scoring.
      Parameters:
      doc - doc being explained.
      subQueryExpl - explanation for the sub-query part.
      valSrcExpls - explanation for the value source part.
      Returns:
      an explanation for the custom score
      Throws:
      IOException

    • customExplain

      public Explanation customExplain(int doc, Explanation subQueryExpl, Explanation valSrcExpl) throws IOException
      Explain the custom score. Whenever overriding customScore(int, float, float), this method should also be overridden to provide the correct explanation for the part of the custom scoring.
      Parameters:
      doc - doc being explained.
      subQueryExpl - explanation for the sub-query part.
      valSrcExpl - explanation for the value source part.
      Returns:
      an explanation for the custom score
      Throws:
      IOException