To: Greg Smith <greg@2ndquadrant.com>
cc: Stephen Frost <sfrost@snowman.net>,
	Euler Taveira de Oliveira <euler@timbira.com>,
	Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PERFORM] pgbench to the MAXINT 
In-reply-to: <4D549E92.4010709@2ndquadrant.com> 
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Comments: In-reply-to Greg Smith <greg@2ndquadrant.com>
	message dated "Thu, 10 Feb 2011 21:27:30 -0500"
Date: Thu, 10 Feb 2011 22:18:38 -0500
Message-ID: <12987.1297394318@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Greg Smith <greg@2ndquadrant.com> writes:
> Poking around a bit more, I just discovered another possible approach is 
> to use erand48 instead of rand in pgbench, which is either provided by 
> the OS or emulated in src/port/erand48.c  That's way more resolution 
> than needed here, given that 2^48 pgbench accounts would be a scale of 
> 2.8M, which makes for a database of about 42 petabytes.

I think that might be a good idea --- it'd reduce the cross-platform
variability of the results quite a bit, I suspect.  random() is not
to be trusted everywhere, but I think erand48 is pretty much the same
wherever it exists at all (and src/port/ provides it elsewhere).

			regards, tom lane