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From: Josh Berkus <josh@agliodbs.com>
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: Aaron Held <aaron@MetroNY.com>,
	Chris Ruprecht <chrup@earthlink.net>, pgsql-sql@postgresql.org
Subject: Re: Performance w/ multiple WHERE clauses
Date: Fri, 20 Sep 2002 14:55:30 -0700
References: <5.1.1.6.2.20020918111926.00a82058@mail.nashlinux.com>
	<200209182039.59437.chrup@earthlink.net>
	<3D8B2C02.8020904@MetroNY.com>
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Message-Id: <200209201455.30054.josh@agliodbs.com>


Aaron,

> 	# SET enable_seqscan to FALSE ;
> 	forced the use of an Index and sped things up greatly.
>=20
> I am not sure why it made the switch.  The load on the server seems to=20
> affect the performance, but I am seeing it more on the production server=
=20
> with 100 million rows as opposed to the development server with only=20
> about 6 million.  I need to buy more drives and develop on a larger data=
=20
> set.

What version are you using?

I'd have 3 suggestions:
1) ANALYZE, ANALYZE, ANALYZE.  Then check if the row estimates made by EXPL=
AIN=20
seem accurate.
2) Modify your postgresql.conf file to raise the cost of seq_scans for pars=
er=20
estimates.
3) Test this all again when 7.3 comes out, as parser estimate improves all =
the=20
time.

--=20
-Josh Berkus
 Aglio Database Solutions
 San Francisco