[jira] Updated: (LUCENE-1302) explain should not mask negative scores

["Doron Cohen (JIRA)" <ji...@apache.org>]

     [ 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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