Date: Sat, 29 Oct 2005 02:12:24 +0200
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
To: pgsql-performance@postgresql.org
Subject: Re: Simple query: how to optimize
Message-ID: <20051029001224.GA6611@uio.no>
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On Fri, Oct 28, 2005 at 03:40:40PM -0700, Roger Hand wrote:
> You're first joining against the entire user table, then filtering out the users
> you don't need.

That's just wrong, sorry -- the planner is perfectly able to push the WHERE
down before the join.

I'd guess the problem is the age() query; age() doesn't really return what
you'd expect, and I don't think it can use an index easily (I might be wrong
here, though). Instead, try something like

  WHERE u.joined_date >= current_date - interval '30 days'

except that if you're running pre-8.0, you might want to precalculate the
right-hand side on the client.

I couldn't see EXPLAIN ANALYZE of your query, BTW -- having it would be
useful.

/* Steinar */
-- 
Homepage: http://www.sesse.net/