From: Tom Lane <tgl@sss.pgh.pa.us>
To: Joachim Wieland <joe@mcknight.de>
Cc: David Wheeler <david@kineticode.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: IMMUTABLE?
Date: Tue, 16 May 2006 09:33:14 -0400
Message-ID: <11508.1147786394@sss.pgh.pa.us> (raw)
In-Reply-To: <20060516094824.GA2376@mcknight.de>
References: <2D4C0FA5-DB75-45EA-91D2-7B4F6DD55083@kineticode.com>
<5211.1147749711@sss.pgh.pa.us>
<3F0CF576-8C6F-433C-9942-BB36F4E1A194@kineticode.com>
<5894.1147753901@sss.pgh.pa.us>
<20060516094824.GA2376@mcknight.de>
Joachim Wieland <joe@mcknight.de> writes:
> So irrespective of caching to prevent evaluation across statements, within a
> single statement, is there a strong reason why for example in
> WHERE col = f(const) with f() declared as immutable or stable and without an
> index on col, f() still gets called for every row? Or is this optimization
> just not done yet?
The above statement is not correct, at least not for immutable functions.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, joe@mcknight.de, david@kineticode.com
Subject: Re: IMMUTABLE?
In-Reply-To: <11508.1147786394@sss.pgh.pa.us>
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