From: Jim C. Nasby <jnasby@pervasive.com>
To: Brendan Duddridge <brendan@clickspace.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Assistance with optimizing query - same SQL, different category_id = Seq Scan
Date: Thu, 11 May 2006 17:08:02 -0500
Message-ID: <20060511220802.GU99570@pervasive.com> (raw)
In-Reply-To: <A8C726F2-AE42-4812-9B71-B6CFE68F18B3@clickspace.com>
References: <A8C726F2-AE42-4812-9B71-B6CFE68F18B3@clickspace.com>
On Mon, May 08, 2006 at 07:29:32PM -0600, Brendan Duddridge wrote:
> Do you have any suggestions on how I can optimize the query so both
> versions of the query come back fast without doing a sequential scan
> on the price table?
Well, before you do anything you should verify that an index scan in the
second case would actually be faster. Set enable_seqscan=off and check
that.
After that, you can favor an index scan by (in order of effectiveness)
increasing the correlation on the appropriate index (by clustering on
it), lowering random_page_cost, or increasing effective_cache_size.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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To: pgsql-performance@postgresql.org
Cc: jnasby@pervasive.com, brendan@clickspace.com
Subject: Re: Assistance with optimizing query - same SQL, different category_id = Seq Scan
In-Reply-To: <20060511220802.GU99570@pervasive.com>
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