Received: from localhost.localdomain (postgresql.org [64.49.215.8])
	by localhost (Postfix) with ESMTP id 936E4475A06
	for <pgsql-sql@postgresql.org>; Thu,  6 Jun 2002 13:01:47 -0400 (EDT)
Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178])
	by postgresql.org (Postfix) with ESMTP id 460BB475B7F
	for <pgsql-sql@postgresql.org>; Thu,  6 Jun 2002 13:01:38 -0400 (EDT)
Received: by megazone.bigpanda.com (Postfix, from userid 1001)
	id 94571D600; Thu,  6 Jun 2002 10:01:37 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1])
	by megazone.bigpanda.com (Postfix) with ESMTP
	id 7FF975C01; Thu,  6 Jun 2002 10:01:37 -0700 (PDT)
Date: Thu, 6 Jun 2002 10:01:37 -0700 (PDT)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Josh Berkus <josh@agliodbs.com>
Cc: Andre Schubert <andre.schubert@km3.de>,
	<pgsql-sql@postgresql.org>
Subject: Re: Indexing timestamps
In-Reply-To: <web-1501412@davinci.ethosmedia.com>
Message-ID: <20020606095611.A27330-100000@megazone23.bigpanda.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Archive-Number: 200206/57
X-Sequence-Number: 8022

On Thu, 6 Jun 2002, Josh Berkus wrote:

> 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.

Unfortunately you can't do that in that sort of syntax.  You'll
need to create a function that returns the month and is marked
as iscachable and use that function in the index creation and
query.