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From "Paul Elschot (JIRA)" <>
Subject [jira] Commented: (LUCENE-1302) explain should not mask negative scores
Date Tue, 10 Jun 2008 16:48:45 GMT


Paul Elschot commented on LUCENE-1302:

I'd like to have Explanation.isMatch() returning true mean that or Scorer.skipTo()
returned true for the explained document score, and to have the Scorer.score() value completely
independent of that.

The javadocs in of the Scorers in the core trunk are consistent about using 'match' this way.

Also, I think there are currently no more backward compatibility issues for this.

> explain should not mask negative scores
> ---------------------------------------
>                 Key: LUCENE-1302
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Query/Scoring
>            Reporter: Doron Cohen
>            Assignee: Doron Cohen
>            Priority: Minor
>             Fix For: 2.4
>         Attachments: lucene-1302-explain-negative.patch
> Explanation.isMatch() returns false for 0 or negative scores. 
> Hence negative scores are omitted from the explanation.
> This causes, when using e.g. BoostingTermQuery with negative boosts, a difference between
the collected doc score and the score shown by explain().  
> A word on the usage of this - BTQ with negative boosts is useful for "punishing" documents
for containing a term. It also allows all sorts of tricks with multiplying query boost by
the BTQ boost, so you get a positive score if both boosts have the same sign but negative
otherwise. - I am sure there other uses as well.

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