Re: Postgres using more memory than it should

From: tv(at)fuzzy(dot)cz
To: "Matthew Wakeling" <matthew(at)flymine(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Postgres using more memory than it should
Date: 2008-12-03 16:25:12
Message-ID: 61517.89.102.139.23.1228321512.squirrel@sq.gransy.com
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>
> Hi. I have a problem on one of our production servers. A fairly
> complicated query is running, and the backend process is using 30 GB of
> RAM. The machine only has 32GB, and is understandably swapping like crazy.
> My colleague is creating swap files as quickly as it can use them up.
>
> The work_mem setting on this machine is 1000MB, running Postgres 8.3.0.

Are you aware that this is a per-session / per-sort settings? That means,
if you have 10 sessions, each of them running query with 2 sort steps in
the plan, it may occupy up to 20 GB of RAM (if both sorts use the whole
1GB of RAM).

regards
Tomas

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