From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Josh Berkus <josh@agliodbs.com>
Cc: Andre Schubert <andre.schubert@km3.de>
Cc: pgsql-sql@postgresql.org
Subject: Re: Indexing timestamps
Date: Thu, 6 Jun 2002 10:01:37 -0700 (PDT)
Message-ID: <20020606095611.A27330-100000@megazone23.bigpanda.com> (raw)
In-Reply-To: <web-1501412@davinci.ethosmedia.com>
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.
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone23.bigpanda.com, josh@agliodbs.com, andre.schubert@km3.de
Subject: Re: Indexing timestamps
In-Reply-To: <20020606095611.A27330-100000@megazone23.bigpanda.com>
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