| From: | Markus Schaber <schabi(at)logix-tt(dot)com> |
|---|---|
| To: | Markus Schaber <schabi(at)logix-tt(dot)com>, PostgreSQL Performance List <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: PostgreSQL underestimates sorting |
| Date: | 2006-11-22 14:28:12 |
| Message-ID: | 45645E7C.4030101@logix-tt.com |
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| Lists: | pgsql-performance |
Hi, Steinar,
Steinar H. Gunderson wrote:
> On Wed, Nov 22, 2006 at 11:17:23AM +0100, Markus Schaber wrote:
>> The Backend allocates gigs of memory (we've set sort_mem to 1 gig), and
>> then starts spilling out more Gigs of temporary data to the disk.
>
> How much RAM is in the server? Remember that sort_mem is _per sort_, so if
> you have multiple sorts, it might allocate several multiples of the amount
> you set up.
That one machine has 16 Gigs of ram, and about 10 Gigs tend to be "free"
/ part of the Linux blocklayer cache.
The temporary data is not swapping, it's the Postgres on-disk sort
algorithm.
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in Europe! www.ffii.org
www.nosoftwarepatents.org
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