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Re: work_mem and shared_buffers

From: "Campbell, Lance" <lance(at)uiuc(dot)edu>
To: "Bill Moran" <wmoran(at)collaborativefusion(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: work_mem and shared_buffers
Date: 2007-11-09 19:05:51
Message-ID: B10E6810AC2A2F4EA7550D072CDE8760197DEA@SAB-FENWICK.sab.uiuc.edu (view raw or flat)
Thread:
Lists: pgsql-performance
Wow.  That is a nice logging feature in 8.3!

Thanks,

Lance Campbell
Project Manager/Software Architect
Web Services at Public Affairs
University of Illinois
217.333.0382
http://webservices.uiuc.edu
 
-----Original Message-----
From: Bill Moran [mailto:wmoran(at)collaborativefusion(dot)com] 
Sent: Friday, November 09, 2007 2:08 PM
To: Campbell, Lance
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] work_mem and shared_buffers

On Fri, 9 Nov 2007 12:08:57 -0600
"Campbell, Lance" <lance(at)uiuc(dot)edu> wrote:

> How do you know when you should up the value of work_mem?  Just play
> with the number.  Is there a query I could do that would tell me if
> PostgreSql is performing SQL that could use more memory for sorting?

8.2 and older, it can be difficult to know, and I don't have a specific
recommendation.

8.3 includes a parameter to log the usage of temporary files by
Postgres.
When a sort can't fit in the available memory, it uses a temp file, thus
you could use this new feature to track when sorts don't fit in
work_mem.

-- 
Bill Moran
Potential Technologies
http://www.potentialtech.com

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