Re: How Postgresql... Some More On That Count thing

From: Mark kirkwood <markir(at)slingshot(dot)co(dot)nz>
To: Shaun Thomas <sthomas(at)townnews(dot)com>
Cc: Sean Chittenden <sean-pgsql-general(at)chittenden(dot)org>, <pgsql-general(at)postgresql(dot)org>
Subject: Re: How Postgresql... Some More On That Count thing
Date: 2001-07-24 10:25:37
Message-ID: 01072422253700.01368@spikey.slithery.org
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Hi Shaun,

Not wanting to turn this into an Oracle list but.... count(rowid) is not
measurably different from count(*) - or count(1).... the problem with these
closed source databases is that we have no idea what the code is doing ( e.g
: is count(*) resolved into count(rowid) , count(1) or something else for
that matter ?), leaving you with the only option of measuring the various
possibilities....and trying to account for your measurement error.

I get - using the current big O release ( 9.0.1 ) on the infamous fact0 table

38 +- 1 s for the lot.

My 2c worth is that this issue consumes too much intellectual energy for very
little gain ( 1/38 x 100 % possible gain at the best.)... there are usually
more productive things to tune for orders of magnitude of reward....

regards and best wishes

Mark

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