Re: in-memory sorting

From: Samuel Gendler <sgendler(at)ideasculptor(dot)com>
To: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: in-memory sorting
Date: 2010-08-19 06:38:50
Message-ID: AANLkTinhNT_QujPGhFoqUX9ts2hW-4whvMOWNBXhwU0=@mail.gmail.com
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Yeah, although with 48GB of available memory and not that much concurrency,
I'm not sure it matters that much. But point taken, I'll see about modifying
the app such that work_mem gets set on a per-query basis.

On Wed, Aug 18, 2010 at 11:24 PM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>wrote:

> On Wed, Aug 18, 2010 at 11:45 PM, Samuel Gendler
> <sgendler(at)ideasculptor(dot)com> wrote:
> > Answered my own question. Cranking work_mem up to 350MB revealed that
> > the in-memory sort requires more memory than the disk sort.
>
> Note that unless you run VERY few client connections, it's usually
> better to leave work_mem somewhere in the 1 to 32Meg range and have
> the connection or user or database that needs 350Meg be set there.
>
> I.e.
>
> <connect>
> set work_mem='512MB';
> <execute query
>
> OR
>
> alter user memoryhog set work_mem='512MB';
>
> OR
>
> alter database memhogdb set work_mem='512MB';
>

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