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@xxxxxxxxxxxxxx
[mailto:pgsql-admin-owner@xxxxxxxxxxxxxx] On Behalf Of Lewis Kapell
Sent: Friday, May 14, 2010 8:34 PM
To: pgsql-admin@xxxxxxxxxxxxxx
Subject: Re: 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@xxxxxxxxxxxx]
Sent: Friday, May 14, 2010 8:18 PM
To: Narasimha Murthy-VRFX87
Cc: pgsql-admin@xxxxxxxxxxxxxx
Subject: RE: Clarification required: autovacuum and VACUUM
command mode
"Narasimha Murthy-VRFX87"<VRFX87@xxxxxxxxxxxx> 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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