Re: speed up query with max() and odd estimates

От: Steinar H. Gunderson
Тема: Re: speed up query with max() and odd estimates
Дата: ,
Msg-id: 20050426204853.GA29424@uio.no
(см: обсуждение, исходный текст)
Ответ на: speed up query with max() and odd estimates  (Matthew Nuzum)
Ответы: Re: speed up query with max() and odd estimates  (Matthew Nuzum)
Re: speed up query with max() and odd estimates  (Matthew Nuzum)
Список: pgsql-performance

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speed up query with max() and odd estimates  (Matthew Nuzum, )
 Re: speed up query with max() and odd estimates  ("Steinar H. Gunderson", )
  Re: speed up query with max() and odd estimates  (Matthew Nuzum, )
  Re: speed up query with max() and odd estimates  (Matthew Nuzum, )
 Re: speed up query with max() and odd estimates  (John A Meinel, )

On Tue, Apr 26, 2005 at 03:16:57PM -0500, Matthew Nuzum wrote:
>  Seq Scan on usage_access  (cost=0.00..1183396.40 rows=12713851
> width=116) (actual time=481796.22..481839.43 rows=3343 loops=1)

That's a gross misestimation -- four orders of magnitude off!

Have you considering doing this in two steps, first getting out whatever
comes from the subquery and then doing the query? Have you ANALYZEd recently?
Do you have an index on atime?

/* Steinar */
--
Homepage: http://www.sesse.net/


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