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https://issues.apache.org/jira/browse/LUCENE-2836?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12975421#action_12975421
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Robert Muir commented on LUCENE-2836:
-------------------------------------
Here's some results from my silly wildcard benchmarker (I think luceneutil
doesnt yet have a keyword title or similar field for this):
(using 10M docs with single valued numeric field, so 10M terms too)
in general its a stupid rewrite method, unless your users are typing in truly
horrific queries and then its better.
||Pattern||no. matching docs||avgms (filter)||avgms (fieldcache)||
|N?N?N?N|1000|35.9|52.5|
|?NNNNNN|10|3.1|44.2|
|??NNNNN|100|5.5|45.6|
|???NNNN|1000|44.7|48.5|
|????NNN|10000|141.8|67.9|
|NN??NNN|100|3.6|41.5|
|NN?N\*|10000|5.3|42.7|
|?NN\*|100000|25.9|50.8|
|\*N|1000000|1639.2|446.8|
|\*N\*|5217031|2089.4|701.2|
|\*NN\*|590040|1811.6|674.8|
> FieldCache rewrite method for MultiTermQueries
> ----------------------------------------------
>
> Key: LUCENE-2836
> URL: https://issues.apache.org/jira/browse/LUCENE-2836
> Project: Lucene - Java
> Issue Type: New Feature
> Reporter: Robert Muir
> Fix For: 4.0
>
> Attachments: LUCENE-2836.patch
>
>
> For some MultiTermQueries, like RangeQuery we have a FieldCacheRangeFilter
> etc (in this case its particularly optimized).
> But in the general case, since LUCENE-2784 we can now have a rewrite method
> to rewrite any MultiTermQuery
> using the FieldCache, because MultiTermQuery's getEnum no longer takes
> IndexReader but Terms, and all the
> FilteredTermsEnums are now just real TermsEnum decorators.
> In cases like low frequency queries this is actually slower (I think this has
> been shown for numeric ranges before too),
> but for the really high-frequency cases like especially ugly wildcards,
> regexes, fuzzies, etc, this can be several times faster
> using the FieldCache instead, since all the terms are in RAM and automaton
> can blast through them quicker.
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