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https://issues.apache.org/jira/browse/LUCENE-1302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12603905#action_12603905
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Hoss Man commented on LUCENE-1302:
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Doron: i haven't looked at your patch, but Explanation.isMatch returns false
for negative scores to be backwards compatible (see LUCENE-605). Any
non-trivial query types where a match can get a non-positive score should be
using a ComplexExplanation.
these comments don't make sense to me...
bq. Another option is for BTQ to return a ComplexExplanation instead of
Explanation and setMatch(true) if the score is non-zero.
...BTQ should call setMatch(true) if it's a "match" (ie: if the doc would be
passed to a HItCollectors collect method) not conditionally based on the score.
bq. Still it would disturb to declare a "negative score" as a "match".
... no idea what you ment there.
> 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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