Message-ID: <45648202.3050109@logix-tt.com>
Date: Wed, 22 Nov 2006 17:59:46 +0100
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
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To: PostgreSQL Performance List <pgsql-performance@postgresql.org>
Subject: Re: PostgreSQL underestimates sorting
References: <456423B3.7010505@logix-tt.com>	<20061122135434.GA9669@uio.no>
	<45645E7C.4030101@logix-tt.com>
	<20061122105341.79874069.frank@wiles.org>
In-Reply-To: <20061122105341.79874069.frank@wiles.org>
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Hi, Frank,

Frank Wiles wrote:


>> The temporary data is not swapping, it's the Postgres on-disk sort
>> algorithm.
> 
>    Are you actually running a query where you have a GB of data
>    you need to sort?  If not I fear you may be causing the system
>    to swap by setting it this high. 

Yes, the table itself is about 40 Gigs in size, thus much larger than
the memory. The machine has 16 Gigs of ram, and 10-12 Gigs are available
for PostgreSQL + Disk Cache.

There's no swapping, only 23 MB of swap are used (40 Gigs are available).

That's one example configuration, there are others on different machines
where it turns out that forcing index usage leads to faster queries, and
less overall ressource consumption. (Or, at least, faster delivery of
the first part of the result so the application can begin to process it
asynchroneously).

Thanks,
Markus

-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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