Re: Clarification required: autovacuum and VACUUM command mode

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(at)postgresql(dot)org
[mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of Lewis Kapell
Sent: Friday, May 14, 2010 8:34 PM
To: pgsql-admin(at)postgresql(dot)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(dot)Grittner(at)wicourts(dot)gov]
> Sent: Friday, May 14, 2010 8:18 PM
> To: Narasimha Murthy-VRFX87
> Cc: pgsql-admin(at)postgresql(dot)org
> Subject: RE: [ADMIN] Clarification required: autovacuum and VACUUM
> command mode
>
> "Narasimha Murthy-VRFX87"<VRFX87(at)motorola(dot)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 Out-of-date statistics are one of the most common causes of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
>

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