From: Craig Ringer <craig@2ndquadrant.com>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Subject: Volatility - docs vs behaviour?
Date: Mon, 30 Jun 2014 17:24:55 +0800
Message-ID: <53B12CE7.5090506@2ndquadrant.com> (raw)
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
Hi all
The docs say:
"For best optimization results, you should label your functions with the
strictest volatility category that is valid for them."
http://www.postgresql.org/docs/current/interactive/xfunc-volatility.html
... but I recall discussion here suggesting that in fact IMMUTABLE
functions may not be inlined where you'd expect, e.g.
http://www.postgresql.org/message-id/CAFj8pRBF3Qr7WtQwO1H_WN=hhFGk0semwhdE+ODz3iyv-TroMQ@mail.gmail....
That's always seemed counter to my expectations. Am I just
misunderstanding? Tom's comment seemed to confirm what Pavel was saying.
I know STRICT can prevent inlining (unfortunately, though necessarily),
but it seems inexplicable that IMMUTABLE should. If it can, then the
documentation is wrong.
Which is it?
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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To: pgsql-performance@postgresql.org
Cc: craig@2ndquadrant.com, tgl@sss.pgh.pa.us, pavel.stehule@gmail.com
Subject: Re: Volatility - docs vs behaviour?
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