To: Martijn van Oosterhout <kleptog@svana.org>
Cc: Simon Riggs <simon@2ndquadrant.com>,
	Ron Peacetree <rjpeace@earthlink.net>, pgsql-hackers@postgresql.org
Subject: Re: [PERFORM] A Better External Sort? 
In-reply-to: <20051004122443.GF17589@svana.org> 
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	<20051002123240.GA30492@svana.org>
	<20051002193835.GJ30492@svana.org>
	<1128376292.8603.142.camel@localhost.localdomain>
	<20051004100441.GC17589@svana.org>
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Comments: In-reply-to Martijn van Oosterhout <kleptog@svana.org>
	message dated "Tue, 04 Oct 2005 14:24:46 +0200"
Date: Tue, 04 Oct 2005 10:06:24 -0400
Message-ID: <7788.1128434784@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Martijn van Oosterhout <kleptog@svana.org> writes:
> A quick binary search puts the cutoff between 1200 and 1300. Given
> version variation I picked a nice round number, 1500.

> Ugh, that's for -O2, for -O3 and above it needs to be 4100 to work.
> Maybe we should go for 5000 or so.

> I'm using: gcc (GCC) 3.3.5 (Debian 1:3.3.5-13)

I don't know what the units of this number are, but it's apparently far
too gcc-version-dependent to consider putting into our build scripts.
Using gcc version 4.0.1 20050727 (current Fedora Core 4 compiler) on
i386, and compiling tuplesort.c as you did, I find:
	-O2: warning goes away between 800 and 900
	-O3: warning is always there (tried values up to 10000000)
(the latter behavior may indicate a bug, not sure).

What's even more interesting is that the warning does not appear in
either case if I omit -finline-limit --- so the default value is plenty.

At least on this particular compiler, the proposed switch would be
counterproductive.

			regards, tom lane