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https://issues.apache.org/jira/browse/LUCENE-1644?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael McCandless updated LUCENE-1644:
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Attachment: LUCENE-1644.patch
Attached patch: fixed some bugs in the last rev, updated test cases,
javadocs, CHANGES. I also optimized MultiTermQueryWrapperFilter to
use the bulk-read API from termDocs.
I confirmed all tests pass if I temporarily switch
CONSTANT_SCORE_FILTER_REWRITE to CONSTANT_SCORE_AUTO_REWRITE_DEFAULT.
I changed QueryParser to use CONSTANT_SCORE_AUTO for rewrite (it was
previously CONSTANT_FILTER).
I still need to run some perf tests to get a rough sense of decent
defaults for CONSTANT_SCORE_AUTO cutover thresholds.
bq. getFilter()/getEnum should stay protected.
OK I made getEnum protected again.
I had tentatively made it public so that one could create their own
[external] rewrite methods. But I think (if we leave it protected),
one could still make an inner/nested class that can access getEnum().
Do we even need getFilter()? I removed it in the patch.
> 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
>
>
> 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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