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https://issues.apache.org/jira/browse/LUCENE-3328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068807#comment-13068807
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Michael Busch commented on LUCENE-3328:
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Nice improvements!
I'm wondering if you considered having ConjunctionTermScorer use the terms' IDF
values to decide which iterator to advance when all are on the same docID? It
should always be best to pick the rarest term.
We've talked about doing that in the past, but it's hard to support this for
any type of subclause, because you'd have to add the ability to estimate the
IDFs of possible subclauses.
But with this change it seems very feasible to try for BQs that only have TQ
clauses.
> Specialize BooleanQuery if all clauses are TermQueries
> ------------------------------------------------------
>
> Key: LUCENE-3328
> URL: https://issues.apache.org/jira/browse/LUCENE-3328
> Project: Lucene - Java
> Issue Type: Improvement
> Components: core/search
> Affects Versions: 3.4, 4.0
> Reporter: Simon Willnauer
> Fix For: 4.0
>
> Attachments: LUCENE-3328.patch, LUCENE-3328.patch, LUCENE-3328.patch
>
>
> During work on LUCENE-3319 I ran into issues with BooleanQuery compared to
> PhraseQuery in the exact case. If I disable scoring on PhraseQuery and bypass
> the position matching, essentially doing a conjunction match,
> ExactPhraseScorer beats plain boolean scorer by 40% which is a sizeable gain.
> I converted a ConjunctionScorer to use DocsEnum directly but still didn't get
> all the 40% from PhraseQuery. Yet, it turned out with further optimizations
> this gets very close to PhraseQuery. The biggest gain here came from
> converting the hand crafted loop in ConjunctionScorer#doNext to a for loop
> which seems to be less confusing to hotspot. In this particular case I think
> code specialization makes lots of sense since BQ with TQ is by far one of the
> most common queries.
> I will upload a patch shortly
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