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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3328) Specialize BooleanQuery if all clauses are TermQueries
Date Thu, 21 Jul 2011 16:43:57 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13069061#comment-13069061
] 

Michael Busch commented on LUCENE-3328:
---------------------------------------

{quote}
The ConjunctionTermScorer sorts the DocsEnums by their frequency in the ctor. The leader will
always be the lowest frequent term in the set. is this what you mean here?
{quote}

Cool, yeah that's roughly what I meant. In general, it's best to always pick the lowest-df
enum as leader:
1) after initialization
2) after a hit was found
3) whenever a doc matched m out of n enums, 1 < m < n

I think what you described covers situation 1), does it also cover 2) and 3)?

> 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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