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.LeafReaderContext), 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 DocValues.

Since:

2.9.2

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field	Description
protected LeafReaderContext	context

Constructor Summary

Constructors

Constructor	Description
CustomScoreProvider(LeafReaderContext context)	Creates a new instance of the provider class for the given IndexReader.

Method Summary

Modifier and Type	Method	Description
Explanation	customExplain(int doc, Explanation subQueryExpl, Explanation valSrcExpl)	Explain the custom score.
Explanation	customExplain(int doc, Explanation subQueryExpl, Explanation[] valSrcExpls)	Explain the custom score.
float	customScore(int doc, float subQueryScore, float valSrcScore)	Compute a custom score by the subQuery score and the FunctionQuery score.
float	customScore(int doc, float subQueryScore, float[] valSrcScores)	Compute a custom score by the subQuery score and a number of FunctionQuery scores.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

context

protected final LeafReaderContext context

Constructor Detail

CustomScoreProvider

public CustomScoreProvider(LeafReaderContext context)

Creates a new instance of the provider class for the given IndexReader.

Method Detail

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