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https://issues.apache.org/jira/browse/LUCENE-4396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14001487#comment-14001487
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Michael McCandless commented on LUCENE-4396:
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{quote}
When terms are few, BooleanNovelScorer performs slower than BS (about -10%).
However, I have to generate tasks with fewer terms and rerun the tasks to
reconfirm
the specific perf. difference.
{quote}
OK, interesting. It may be BooleanNovelScorer doesn't work out, and we "just"
focus on BooleanScorer handling MUST.
{quote}
bq. but you commented this out in your patch in order to test NBS I guess?
yes, I did that in order to test BNS. Otherwise, luceneutil would throw
exception.
{quote}
OK, maybe add a comment just saying something "temporarily commented out so
NovelBS is invoked instead of BS"? And what exception did luceneutil throw...?
bq. Hmm, I haven't carried out such experiment yet. Checking the perf. results
of BS vs BS2
is a good idea. I will do that.
Thank you!
> BooleanScorer should sometimes be used for MUST clauses
> -------------------------------------------------------
>
> Key: LUCENE-4396
> URL: https://issues.apache.org/jira/browse/LUCENE-4396
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Attachments: AndOr.tasks, LUCENE-4396.patch, LUCENE-4396.patch,
> LUCENE-4396.patch, LUCENE-4396.patch, luceneutil-score-equal.patch
>
>
> Today we only use BooleanScorer if the query consists of SHOULD and MUST_NOT.
> If there is one or more MUST clauses we always use BooleanScorer2.
> But I suspect that unless the MUST clauses have very low hit count compared
> to the other clauses, that BooleanScorer would perform better than
> BooleanScorer2. BooleanScorer still has some vestiges from when it used to
> handle MUST so it shouldn't be hard to bring back this capability ... I think
> the challenging part might be the heuristics on when to use which (likely we
> would have to use firstDocID as proxy for total hit count).
> Likely we should also have BooleanScorer sometimes use .advance() on the subs
> in this case, eg if suddenly the MUST clause skips 1000000 docs then you want
> to .advance() all the SHOULD clauses.
> I won't have near term time to work on this so feel free to take it if you
> are inspired!
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