| From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
|---|---|
| To: | Brendan Duddridge <brendan(at)clickspace(dot)com> |
| Cc: | PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Assistance with optimizing query - same SQL, different category_id = Seq Scan |
| Date: | 2006-05-11 22:08:02 |
| Message-ID: | 20060511220802.GU99570@pervasive.com |
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| Lists: | pgsql-performance |
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(at)pervasive(dot)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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