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From "Hoss Man (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1302) explain should not mask negative scores
Date Tue, 10 Jun 2008 16:58:45 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12603929#action_12603929
] 

Hoss Man commented on LUCENE-1302:
----------------------------------

FWIW: Paul's comment is exactly what i was trying to get at.

The only reason Explaination.isMatch returns true for positive scores without requiring that
the match state be specified explicitly was is so it would be backwards compatible for older
legacy query types (possibly created by lucene users) when the match/score semantics where
clarified in order to allow/support negative scores for matching documents.





> explain should not mask negative scores
> ---------------------------------------
>
>                 Key: LUCENE-1302
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1302
>             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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