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Re: Postgres not using indexes

From: Lawrence Cohan <LCohan(at)web(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, "pgsql-bugs(at)postgresql(dot)org"<pgsql-bugs(at)postgresql(dot)org>
Subject: Re: Postgres not using indexes
Date: 2011-03-30 16:53:23
Message-ID: 965AA5440EAC094E9F722519E285ACEDAC5E66A556@WWCEXCHANGE.web.web.com (view raw or flat)
Thread:
Lists: pgsql-bugs
We thank you for the links that have a lots of info and please note that we tuned our servers as recommended by Enterprise DB experts while they were in house for our hardware/software migrations and the setting you mentioned are in place already.

Regards,
Lawrence Cohan.

-----Original Message-----
From: Kevin Grittner [mailto:Kevin(dot)Grittner(at)wicourts(dot)gov]
Sent: March-30-11 12:45 PM
To: pgsql-bugs(at)postgresql(dot)org; Lawrence Cohan
Subject: Re: [BUGS] Postgres not using indexes

Lawrence Cohan <LCohan(at)web(dot)com> wrote:

> We have a huge performance issues in Postgres that surfaced due to
> existing indexes not being used

This doesn't sound like a bug; it sounds like you haven't tuned your
server.

For starters, you should check out this page:

http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server

As a quick try, you could issue these statements on the connection
right before one of the problem queries:

set effective_cache_size = '7GB';
  -- use 1 or 2 GB less than RAM on the machine
set random_page_cost = 2;
-- now try your query

If, after reading the above-cited page and tuning your server you
still have performance problems, pick one query to work on first,
and follow the step outlined here:

http://wiki.postgresql.org/wiki/SlowQueryQuestions

Use the pgsql-performance list for performance issues, not the bugs
list.  You'll find more people who will be able to help you with
performance issues there.

-Kevin

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