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https://issues.apache.org/jira/browse/LUCENE-4396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13937412#comment-13937412
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Da Huang commented on LUCENE-4396:
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I'm revising and polishing my proposal these days, and I have discovered a
interesting thing. That is: if BooleanScorer supports required scorers in the
way I have proposed, docIDs would be in acsending order in the bucket table. I
think this can make BooleanScorer be a Not-Top Scorer, as .advance() .docID()
.nextDoc() etc. can be implemented. However, I'm not sure how it would affect
the performance when it acts as a Not-Top Scorer. This is because when
.nextDoc() or .advance() is called, BooleanScorer may calculate a 2K window
whose data may not be all useful.
I hope I have made my idea clear.
> 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
>
> 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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