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From "Robert Muir (JIRA)" <>
Subject [jira] Commented: (LUCENE-2836) FieldCache rewrite method for MultiTermQueries
Date Mon, 03 Jan 2011 13:30:45 GMT


Robert Muir commented on LUCENE-2836:

OK, I'll work on getting it into contrib. 

I think its best to put it there because its generally slower (only faster in certain circumstances),

and at the moment the app has to supply the 'query planning logic' to make good use of it.

> FieldCache rewrite method for MultiTermQueries
> ----------------------------------------------
>                 Key: LUCENE-2836
>                 URL:
>             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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