Re: Unexpected query plan results

On Fri, May 29, 2009 at 1:30 PM, Dave Dutcher <dave(at)tridecap(dot)com> wrote:

> > From: Anne Rosset
> > Subject: Re: [PERFORM] Unexpected query plan results
> > >
> > >
> > Thank Dave. We are using postgresql-server-8.2.4-1PGDG and
> > have work-mem set to 20MB.
> > What value would you advise?
> > thanks,
> >
> > Anne
>
>
> Work-mem is kind of tricky because the right setting depends on how much
> ram
> your machine has, is the machine dedicated to postgres, and how many
> simultaneous connections you have. If this is a test server, and not used
> in production, you could just play around with the setting and see if your
> query gets any faster.

Right, the trick to remember is that you could possibly end up in a
scenario where you have max_connections * work_mem being used just for
sorting / joins and the rest of your memory will be swapped, so be careful
not to push too high. Also, work_mem is not going to be fully allocated at
fork time, it'll only use up to that much as needed.

--Scott

>
> Here are the docs on work mem
>
>
> http://www.postgresql.org/docs/8.2/interactive/runtime-config-resource.html#
> RUNTIME-CONFIG-RESOURCE-MEMORY
>
>
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