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