Received: from localhost.localdomain (postgresql.org [64.49.215.8])
	by localhost (Postfix) with ESMTP id 583B5475B98
	for <pgsql-sql@postgresql.org>; Thu, 16 May 2002 18:22:07 -0400 (EDT)
Received: from joeconway.com (unknown [63.210.180.150])
	by postgresql.org (Postfix) with ESMTP id 48B12475AA7
	for <pgsql-sql@postgresql.org>; Thu, 16 May 2002 18:22:03 -0400 (EDT)
Received: from [206.19.64.3] (account jconway HELO joeconway.com)
	by joeconway.com (CommuniGate Pro SMTP 3.5.6)
	with ESMTP-TLS id 413052; Thu, 16 May 2002 14:16:06 -0700
Message-ID: <3CE4310C.8030302@joeconway.com>
Date: Thu, 16 May 2002 15:22:04 -0700
From: Joe Conway <mail@joeconway.com>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US;
	rv:0.9.9) Gecko/20020311
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: josh@agliodbs.com
Cc: pgsql-sql@postgresql.org
Subject: Re: How can I tell the performance difference?
References: <200205161429.50058.josh@agliodbs.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-Archive-Number: 200205/181
X-Sequence-Number: 7816

Josh Berkus wrote:
> Folks,
> 
> I have a view which will be used very, very often in my database.  As such, I 
> need to evaluate which of the two following structures is the best for that 
> view.  However, I can't easily figure out which of the two explain plans 
> looks more costly.  Can anybody help?
> 

I would use PHP (or Perl or something) to generate some sample data 
(i.e. a few hundred thousand records or so) and then use EXPLAIN ANALYZE 
(after VACUUM ANALYZE of course ;-) ), instead of trying to guess 
performance based on EXPLAIN output that won't be relevant once you have 
data.

Just my 2 cents . . .

Joe