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From: "Josh Berkus" <josh@agliodbs.com>
Subject: Re: Indexing timestamps
To: Andre Schubert <andre.schubert@km3.de>, pgsql-sql@postgresql.org
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Date: Thu, 06 Jun 2002 09:02:21 -0700
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Andre,

I'm not even going to try to deal with the seq_scan vs. index_scan
issues on now().  This has been brought up in the list archives.  Test
your actual response times as well as the query plan; you may find that
you don't have a real problem.

Something I can help you with:

> explain select * from test_table where date_trunc('month',time_stamp)
> = date_trunc('month',datetime('2002-01-01'));
> NOTICE:  QUERY PLAN:
> 
> Seq Scan on test_table  (cost=0.00..2441.41 rows=584 width=16)

Try doing a:
CREATE INDEX idx_test_month ON test_table(extract(month FROM
time_stamp));

Which should help.

-Josh