> I also
> enforced the index scan and compared with forbidding the index scan.
The
> result was on my more realistic examples that both versions performed
quite
> the same.  There was no *real* difference. For sure in this simple
query there
> is a difference but the real examples showed only 2% - 5% speed
increase
> (if not slower with enforcing index scans!).

You could somewhat speed up the query if you avoid that the sort
hits the disk. A simple test here showed, that you need somewhere
near sort_mem = 15000 in postgresql.conf.

Andreas

Tue, 30 Oct 2001 12:29:50 +0100
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>
Re: Serious performance problem
On Tue, 30 Oct 2001, Zeugswetter Andreas SB SD wrote:

> You could somewhat speed up the query if you avoid that the sort
> hits the disk. A simple test here showed, that you need somewhere
> near sort_mem = 15000 in postgresql.conf.
Well this are the usual hints from pgsql-general.  I did so and
increased step by step to:

   shared_buffers = 131072
   sort_mem       = 65536

This lead to a double of speed in my tests but this are settings where
an enhancement of memory doesnï¿½t result in a speed increase any more.

When I was posting my question here I was talking about this "tuned"
PostgreSQL server.  The default settings where even worse!

Kind regards

        Andreas.

Tue, 30 Oct 2001 13:46:22 +0100 (CET)
"Tille, Andreas" <TilleA@rki.de>
Re: Serious performance problem