Re: Binary search in ScalarArrayOpExpr for OR'd constant arrays
От | Tomas Vondra |
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Тема | Re: Binary search in ScalarArrayOpExpr for OR'd constant arrays |
Дата | |
Msg-id | 20200423124700.xclyoq7qxtlvjvxs@development обсуждение исходный текст |
Ответ на | Binary search in ScalarArrayOpExpr for OR'd constant arrays (James Coleman <jtc331@gmail.com>) |
Ответы |
Re: Binary search in ScalarArrayOpExpr for OR'd constant arrays
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Список | pgsql-hackers |
On Mon, Apr 20, 2020 at 09:27:34PM -0400, James Coleman wrote: >Over in "execExprInterp() questions / How to improve scalar array op >expr eval?" [1] I'd mused about how we might be able to optimized >scalar array ops with OR'd semantics. > >This patch implements a binary search for such expressions when the >array argument is a constant so that we can avoid needing to teach >expression execution to cache stable values or know when a param has >changed. > >The speed-up for the target case can pretty impressive: in my >admittedly contrived and relatively unscientific test with a query in >the form: > >select count(*) from generate_series(1,100000) n(i) where i in (<1000 >random integers in the series>) > >shows ~30ms for the patch versus ~640ms on master. > Nice improvement, although 1000 items is probably a bit unusual. The threshold used in the patch (9 elements) seems a bit too low - what results have you seen with smaller arrays? Another idea - would a bloom filter be useful here, as a second optimization? That is, for large arrays build s small bloom filter, allowing us to skip even the binary search. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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