From: Richard Huxton <dev@archonet.com>
To: Mark Kirkwood <markir@paradise.net.nz>
Cc: Kurt Overberg <kurt@hotdogrecords.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Weird 8.2.4 performance
Date: Thu, 07 Jun 2007 10:23:19 +0100
Message-ID: <4667CE87.30101@archonet.com> (raw)
In-Reply-To: <46674AEF.6040803@paradise.net.nz>
References: <371D1936-E96B-4865-AEEF-C82AC41C2982@hotdogrecords.com>
<46674AEF.6040803@paradise.net.nz>
Mark Kirkwood wrote:
>
> 8.2 is deciding to use a bitmap index scan on taskid_taskinstance_key,
> which seems to be slower (!) than a plain old index scan that 8.0 is
> using. A dirty work around is to disable bitmap scans via:
I'm having difficulty figuring out why it's doing this at all. There's
only one index involved, and it's over the primary-key to boot!
An EXPLAIN ANALYSE with enable_bitmapscan off should say why PG thinks
the costs are cheaper than they actually are.
PS - well worded question Kurt. All the relevant information neatly laid
out, explain analyse on both platforms - you should be charging to let
people help ;-)
--
Richard Huxton
Archonet Ltd
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To: pgsql-performance@postgresql.org
Cc: dev@archonet.com, markir@paradise.net.nz, kurt@hotdogrecords.com
Subject: Re: Weird 8.2.4 performance
In-Reply-To: <4667CE87.30101@archonet.com>
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