Re: Clarification required: autovacuum and VACUUM command mode
От | Lewis Kapell |
---|---|
Тема | Re: Clarification required: autovacuum and VACUUM command mode |
Дата | |
Msg-id | 4BED6B46.2090109@setonhome.org обсуждение исходный текст |
Ответ на | Re: Clarification required: autovacuum and VACUUM command mode ("Narasimha Murthy-VRFX87" <VRFX87@motorola.com>) |
Список | pgsql-admin |
Yes, the query planner is part of Postgres itself. Here are some pages of the manual that talk about the planner and how it works: http://www.postgresql.org/docs/8.3/static/using-explain.html http://www.postgresql.org/docs/8.3/static/planner-stats.html And this talks about configuration options to control (or at least influence) what the planner does: http://www.postgresql.org/docs/8.3/static/runtime-config-query.html - Lewis On 5/14/2010 11:17 AM, Narasimha Murthy-VRFX87 wrote: > Hi Lewis, > > Thanks for the clarification. > > Referring to the statement in postgresql-8.2-US.pdf document "ANALYZE > collects statistics about the contents of tables in the database ... > query planner uses these statistics to help determine the most efficient > execution plans for queries." > > From your response, I now understood that "Query planner" is part of > PostgreSQL DB. > > Regards, Narasimha Murthy > Cell +91 95814 98895, +91-94940 62794 | 040-2347 2025 (O) | x2025 (O) > > -----Original Message----- > From: pgsql-admin-owner@postgresql.org > [mailto:pgsql-admin-owner@postgresql.org] On Behalf Of Lewis Kapell > Sent: Friday, May 14, 2010 8:34 PM > To: pgsql-admin@postgresql.org > Subject: Re: [ADMIN] Clarification required: autovacuum and VACUUM > command mode > > You misunderstand the purpose of ANALYZE. Postgres needs the results in > order to perform queries efficiently. Whether you have the ability to > change or tune the queries is beside the point. > > - Lewis > > > On 5/14/2010 11:01 AM, Narasimha Murthy-VRFX87 wrote: >> Hi Kevin, >> >> Thanks again for a quick response. >> >> I am using a 3rd party application, which in turn using PostgreSQL DB. > >> I can not change/tune the SQL queries, performed by the 3rd party >> application. Hence, the statistics generated by ANALYZE, is of no use >> to me. That is the reason, I have planned not to run ANALYZE. >> >> Regards, Narasimha Murthy >> Cell +91 95814 98895, +91-94940 62794 | 040-2347 2025 (O) | x2025 (O) >> >> -----Original Message----- >> From: Kevin Grittner [mailto:Kevin.Grittner@wicourts.gov] >> Sent: Friday, May 14, 2010 8:18 PM >> To: Narasimha Murthy-VRFX87 >> Cc: pgsql-admin@postgresql.org >> Subject: RE: [ADMIN] Clarification required: autovacuum and VACUUM >> command mode >> >> "Narasimha Murthy-VRFX87"<VRFX87@motorola.com> wrote: >> >>> Another query: I do not want to run Analyze. However, auto-vacuum >>> runs >> >>> both both VACUUM and ANALYZE. I do not see any option to disable >>> running ANALYZE during auto-vacuum. Is there any way to achive this? >> >> Usually it's best to run ANALYZE more often than VACUUM, since the >> statistics generated by ANALYZE are used to choose the most efficient >> plan, and ANALYZE runs faster because it just takes a random sample of > >> rows. Out-of-date statistics are one of the most common causes of >> slow queries. That's not to say there couldn't be some very unusual >> circumstances under which it might make sense to disable ANALYZE, but >> I'm highly skeptical. >> >> Anyway, if you *really* want to shoot that fly off the end of your toe > >> (to stretch a metaphor), you could adjust the autovacuum settings >> related to analyze to really high values. >> >> -Kevin >> > > > -- > Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org) To make > changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-admin >
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