From: Luke Lonergan <llonergan@greenplum.com>
To: Glenn Sullivan <glenn.sullivan@varianinc.com>
To: pgsql-performance@postgresql.org
Subject: Re: Performance of ORDER BY
Date: Tue, 05 Dec 2006 09:36:44 -0800
Message-ID: <C19AEE2C.F553%llonergan@greenplum.com> (raw)
In-Reply-To: <4575A863.6040504@varianinc.com>
Glenn,
On 12/5/06 9:12 AM, "Glenn Sullivan" <glenn.sullivan@varianinc.com> wrote:
> I am wanting some ideas about improving the performance of ORDER BY in
> our use. I have a DB on the order of 500,000 rows and 50 columns.
> The results are always sorted with ORDER BY. Sometimes, the users end up
> with a search that matches most of the rows. In that case, I have a
> LIMIT 5000 to keep the returned results under control. However, the
> sorting seems to take 10-60 sec. If I do the same search without the
> ORDER BY, it takes about a second.
>
> I am currently on version 8.0.1 on Windows XP using a Dell Optiplex 280
> with 1Gb of ram. I have set sort_mem=100000 set.
>
> Any ideas?
Upgrade to 8.1 or 8.2, there were very large performance improvements to the
sort code made for 8.1+. Also, when you've upgraded, you can experiment
with increasing work_mem to get better performance. At some value of
work_mem (probably > 32MB) you will reach a plateau of performance, probably
4-5 times faster than what you see with 8.0.
- Luke
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To: pgsql-performance@postgresql.org
Cc: llonergan@greenplum.com, glenn.sullivan@varianinc.com
Subject: Re: Performance of ORDER BY
In-Reply-To: <C19AEE2C.F553%llonergan@greenplum.com>
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