From: Mischa Sandberg <mischa@ca.sophos.com>
To: pgsql-performance@postgresql.org
Subject: Re: Bad plan for join to aggregate of join.
Date: Tue, 12 Sep 2006 17:51:27 -0700
Message-ID: <4507560F.9020906@ca.sophos.com> (raw)
In-Reply-To: <3215.1158104550@sss.pgh.pa.us>
References: <821wqiy0oc.fsf@mid.bfk.de>
<45071FCC.8090509@ca.sophos.com>
<3215.1158104550@sss.pgh.pa.us>
Tom Lane wrote:
> Mischa Sandberg <mischa@ca.sophos.com> writes:
>> can PG see that a join on an grouped-by field
>> can be pushed down into the query as an indexable filter?
>
> No. The GROUP BY serves as a partial optimization fence. If you're
> concerned about the speed of this query, I recommend making a different
> view in which 'message' is joined inside the GROUP BY.
Thanks.
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: mischa@ca.sophos.com
Subject: Re: Bad plan for join to aggregate of join.
In-Reply-To: <4507560F.9020906@ca.sophos.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox