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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1644) Enable MultiTermQuery's constant score mode to also use BooleanQuery under the hood
Date Thu, 23 Jul 2009 13:25:14 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1644?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12734592#action_12734592
] 

Uwe Schindler commented on LUCENE-1644:
---------------------------------------

You were faster. The problem was the missing update of term count. I first thought, that you
maybe counting the terms two times (one time at the beginning and then again in the filter,
if the auto mode switches). But you are now only updating the term count at the end when you
build the boolean query.

By the way: How about initializing the ArrayList not with the default size, but maybe termCount
cutoff/2 or something like that?

> Enable MultiTermQuery's constant score mode to also use BooleanQuery under the hood
> -----------------------------------------------------------------------------------
>
>                 Key: LUCENE-1644
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1644
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.9
>
>         Attachments: LUCENE-1644.patch, LUCENE-1644.patch, LUCENE-1644.patch, LUCENE-1644.patch,
LUCENE-1644.patch, LUCENE-1644.patch
>
>
> When MultiTermQuery is used (via one of its subclasses, eg
> WildcardQuery, PrefixQuery, FuzzyQuery, etc.), you can ask it to use
> "constant score mode", which pre-builds a filter and then wraps that
> filter as a ConstantScoreQuery.
> If you don't set that, it instead builds a [potentially massive]
> BooleanQuery with one SHOULD clause per term.
> There are some limitations of this approach:
>   * The scores returned by the BooleanQuery are often quite
>     meaningless to the app, so, one should be able to use a
>     BooleanQuery yet get constant scores back.  (Though I vaguely
>     remember at least one example someone raised where the scores were
>     useful...).
>   * The resulting BooleanQuery can easily have too many clauses,
>     throwing an extremely confusing exception to newish users.
>   * It'd be better to have the freedom to pick "build filter up front"
>     vs "build massive BooleanQuery", when constant scoring is enabled,
>     because they have different performance tradeoffs.
>   * In constant score mode, an OpenBitSet is always used, yet for
>     sparse bit sets this does not give good performance.
> I think we could address these issues by giving BooleanQuery a
> constant score mode, then empower MultiTermQuery (when in constant
> score mode) to pick & choose whether to use BooleanQuery vs up-front
> filter, and finally empower MultiTermQuery to pick the best (sparse vs
> dense) bit set impl.

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