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From "Doron Cohen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-1302) explain should not mask negative scores
Date Tue, 10 Jun 2008 13:26:45 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1302?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Doron Cohen updated LUCENE-1302:
--------------------------------

    Attachment: lucene-1302-explain-negative.patch

With this patch isMatch() returns false only for score == zero .
All tests pass.
It does disturb though to announce a negative score as a "match".
So, while this patch easily makes things work with negative scores, a better fix may be to
leave isMatch() as is, but modify calls to it that are meant to decide if the questioned explanation
should be included in the constructed explanation by a test of the score, or perhaps a specific
new method e.g. isInformative(). 


> 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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