To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Greg Stark <gsstark@mit.edu>,  Mark Kirkwood <markir@paradise.net.nz>,
	Luke Lonergan <llonergan@greenplum.com>,  stange@rentec.com,
	Dave Cramer <pg@fastcrypt.com>,  Joshua Marsh <icub3d@gmail.com>,
	pgsql-performance@postgresql.org
Subject: Re: Hardware/OS recommendations for large databases (
References: <BFAAB702.1460D%llonergan@greenplum.com>
	<438583C8.4050809@paradise.net.nz> <87d5kqkpd2.fsf@stark.xeocode.com>
	<14286.1132849528@sss.pgh.pa.us>
In-Reply-To: <14286.1132849528@sss.pgh.pa.us>
From: Greg Stark <gsstark@mit.edu>
Organization: The Emacs Conspiracy; member since 1992
Date: 24 Nov 2005 11:40:21 -0500
Message-ID: <877jayknii.fsf@stark.xeocode.com>
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> Greg Stark <gsstark@mit.edu> writes:
> > Last I heard the reason count(*) was so expensive was because its state
> > variable was a bigint. That means it doesn't fit in a Datum and has to be
> > alloced and stored as a pointer. And because of the Aggregate API that means
> > it has to be allocated and freed for every tuple processed.
> 
> There's a hack in 8.1 to avoid the palloc overhead (courtesy of Neil
> Conway IIRC).

ah, cool, missed that.

-- 
greg