Re: Slow SQL query (14-15 seconds)

От: Tom Lane
Тема: Re: Slow SQL query (14-15 seconds)
Дата: ,
Msg-id: 5163.1226583110@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Slow SQL query (14-15 seconds)  (Bruno Baguette)
Ответы: Re: Slow SQL query (14-15 seconds)  (Bruno Baguette)
Список: pgsql-performance

Скрыть дерево обсуждения

Slow SQL query (14-15 seconds)  (Bruno Baguette, )
 Re: Slow SQL query (14-15 seconds)  (Matthew Wakeling, )
  Re: Slow SQL query (14-15 seconds)  (Bruno Baguette, )
 Re: Slow SQL query (14-15 seconds)  (Tom Lane, )
  Re: Slow SQL query (14-15 seconds)  (Bruno Baguette, )
   Re: Slow SQL query (14-15 seconds)  (Tom Lane, )
 Re: Slow SQL query (14-15 seconds)  (Tomasz Myrta, )
 Re: Slow SQL query (14-15 seconds)  ("Vladimir Sitnikov", )
  Re: Slow SQL query (14-15 seconds)  (Bruno Baguette, )

Bruno Baguette <> writes:
> I'm having a problem with this query (below) that takes betweend 14 and
> 15 seconds to run, which is too long for the end-user.
> I've done a EXPLAIN ANALYZE (below below) but I'm having difficulties to
> see which part of that query is taking so many times.

It's the repeatedly executed EXISTS subplan that's hurting you:

>                             SubPlan
>                               ->  Nested Loop  (cost=35.56..378.16
> rows=2 width=0) (actual time=16.511..16.511 rows=0 loops=818)

16.511 * 818 = 13505.998, so this is all but about 100 msec of the
runtime.  Can't tell if there's any easy way to improve it.  In
pre-8.4 releases trying to convert the EXISTS into an IN might help.

            regards, tom lane


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