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https://issues.apache.org/jira/browse/LUCENE-4396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13985254#comment-13985254
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Da Huang commented on LUCENE-4396:
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Thanks for your suggestions, Mike. And sorry for my late reply.
{quote}
Hmm, the patch didn't cleanly apply, but I was able to work through
it. I think your dev area is not up to date with trunk?
{quote}
I haven't merged my branch to the newest trunk version, because my network
account at school for April has been run out and I couldn't pull the code from
github untill 1 May. Sorry for that.
{quote}
Small code style things
{quote}
I'm very sorry for the code style. That's my fault. Very sorry for that.
{quote}
So it looks like BooleanNovelScorer is able to be a Scorer because the
linked-list of visited buckets in one window are guaranteed to be in
docID order, because we first visit the requiredConjunctionScorer's
docs in that window.
{quote}
Yes, you're right.
{quote}
Have you tested performance when the .advance method here isn't called?
Ie, just boolean queries w/ one MUST and one or more SHOULD?
{quote}
No, I haven't. Do you mean the .advance method of subScorers in
BooleanNovelScorer?
If so, I will do that.
If you mean the .advance method of BooleanNovelScorer itself, I think it would
be confusing,
because BooleanNovelScorer now is used when there's at least one MUST clause,
no matter whether it acts as a top scorer or not. Therefore, .advance() of
BooleanNovelScorer
must be called when BooleanNovelScorer acts as a non-top scorer.
{quote}
I think the important question here is whether/in what cases the
BooleanNovelScorer approach beats BooleanScorer2 performance?
{quote}
Yes, you're right. But BooleanNovelScorer has not been totally finished, and
the performance itself
remans to be improved especially its .advance method.
{quote}
I realized LUCENE-4872 is related here, i.e. we should also sometimes
use BooleanScorer for the minShouldMatch>1 case.
{quote}
Yes, I also notice that. :) I think this issue should be dealed with together.
> 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: LUCENE-4396.patch, LUCENE-4396.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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