| From: | Richard Huxton <dev(at)archonet(dot)com> |
|---|---|
| To: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz> |
| Cc: | Kurt Overberg <kurt(at)hotdogrecords(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Weird 8.2.4 performance |
| Date: | 2007-06-07 09:23:19 |
| Message-ID: | 4667CE87.30101@archonet.com |
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| Lists: | pgsql-performance |
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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