From: Jim Nasby <Jim.Nasby@BlueTreble.com>
To: David G. Johnston <david.g.johnston@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Karl Czajkowski <karlcz@isi.edu>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: optimizing immutable vs. stable function calls?
Date: Mon, 23 Jan 2017 09:10:00 -0600
Message-ID: <74793a73-20ac-0e1f-bb61-cafe6b3371cf@BlueTreble.com> (raw)
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On 1/18/17 6:09 PM, David G. Johnston wrote:
> That would not be a productive exercise for me, or most people who just
> want
> some idea of what to expect in terms of behavior when they write and use a
> Stable function (Immutable and Volatile seem fairly easy to reason about).
Yeah, this isn't an uncommon question for users to have, and "read the
code" isn't a great answer.
If there's a README or comment block that describes this, that might be
a reasonable compromise.
It would certainly be useful to document how to push the planner in the
right direction as well. I didn't realize that SELECT ... (SELECT
slow_stable_function()) was a thing until reading this thread.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
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Cc: Jim.Nasby@BlueTreble.com, david.g.johnston@gmail.com, tgl@sss.pgh.pa.us, karlcz@isi.edu
Subject: Re: optimizing immutable vs. stable function calls?
In-Reply-To: <74793a73-20ac-0e1f-bb61-cafe6b3371cf@BlueTreble.com>
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