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?
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: Heikki Linnakangas [mailto:hlinnaka@gmail.com] On Behalf Of Heikki
Linnakangas
Sent: Friday, November 09, 2007 11:57 AM
To: Campbell, Lance
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] work_mem and shared_buffers
Campbell, Lance wrote:
> Does the amount of memory allocate to work_mem get subtracted from
> shared_buffers?
>
> Example:
>
> If work_mem is 1M and there are 10 connections and shared_buffers is
> 100M then would the total be 90 M left for shared_buffers?
>
> Or does the amount of memory allocated for work_mem have nothing to do
> with shared_buffers?
No, they're completely separate.
Note that a connection can use more than work_mem of memory. For
example, if you run a query with multiple Sort or hash-nodes, each such
node allocates up to work_mem of memory.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
