From: Josh Berkus <josh@agliodbs.com>
To: Brendan Jurd <direvus@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Constraint exclusion can't process simple constant expressions?
Date: Wed, 20 Apr 2011 19:13:07 -0700
Message-ID: <4DAF92B3.60806@agliodbs.com> (raw)
In-Reply-To: <BANLkTinY9G33LEsnLmWbkR0j3TcxX+HGug@mail.gmail.com>
References: <4DAF70FD.7000609@agliodbs.com>
<26139.1303346929@sss.pgh.pa.us>
<4DAF8F60.9050407@agliodbs.com>
<BANLkTinY9G33LEsnLmWbkR0j3TcxX+HGug@mail.gmail.com>
> Emphasis on "always". If the result of the function, given the same
> argument values, can be different after a SET, then it doesn't qualify
> for immutability. At least, that's my understanding.
Hmmmm. But within the context of the query plan itself, the results of
that expression are going to be constant. That is, for a given query
execution, it's always going to be the same comparison.
So this goes back to my original assertion that CE can't be fixed ...
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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: josh@agliodbs.com, direvus@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: Constraint exclusion can't process simple constant expressions?
In-Reply-To: <4DAF92B3.60806@agliodbs.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