Message-ID: <53B12CE7.5090506@2ndquadrant.com>
Date: Mon, 30 Jun 2014 17:24:55 +0800
From: Craig Ringer <craig@2ndquadrant.com>
Organization: 2nd Quadrant
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To: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
CC: Tom Lane <tgl@sss.pgh.pa.us>, Pavel Stehule <pavel.stehule@gmail.com>
Subject: Volatility - docs vs behaviour?
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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.com

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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