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Re: [PERFORMANCE] work_mem vs temp files issue

From: decibel <decibel(at)decibel(dot)org>
To: Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>
Cc: psql performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: [PERFORMANCE] work_mem vs temp files issue
Date: 2009-09-13 22:12:19
Message-ID: B43373EF-4CFC-4643-AB6E-5BC0D4A7EB58@decibel.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Aug 19, 2009, at 7:45 PM, Jaime Casanova wrote:
> AFAIUI, work_mem is used for some operations (sort, hash, etc) for
> avoiding the use of temp files on disk...
>
> In a client server i'm monitoring (pg 8.3.7, 32GB of ram) work_mem is
> set to 8MB, however i'm seeing a lot of temp files (>30000 in 4 hours)
> with small sizes (ie: 2021520 obviously lower than 8MB). so, why?
> maybe we use work_mem until we find isn't enough and we send just the
> difference to a temp file?
>
> i'm not thinking in raising work_mem until i understand this well,
> what's the point if we still create temp files that could fit in
> work_mem...


Are you using temp tables? Those end up in pgsql_tmp as well.
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828



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