Re: 8.2rc1 (much) slower than 8.2dev?

From: Arjen van der Meijden <acmmailing(at)tweakers(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: 8.2rc1 (much) slower than 8.2dev?
Date: 2006-12-04 16:41:14
Message-ID: 45744FAA.20603@tweakers.net
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Tom Lane wrote:
> Arjen van der Meijden <acmmailing(at)tweakers(dot)net> writes:
>> I'll run another analyze on the database to see if that makes any
>> difference, but after that I'm not sure what to check first to figure
>> out where things go wrong?
>
> Look for changes in plans?

Yeah, there are a few number of small changes in plans and costs
estimated. I've a large list of queries executed against both databases,
and I haven't seen any differences in row-estimates, so the analyze's
have yielded similar enough results.

I'm not sure whether some of the changes are for better or worse, you
can probably spot that a bit faster than I can. I saw a few index scans
replaced by seq scans (on small tables), all index scans seem to have
doubled in cost? And I saw a few bitmap scans in stead of normal index
scans and more such small changes. But not so small if you execute a
hundreds of thousands of those queries.

Since I'd rather not send the entire list of queries to the entire
world, is it OK to send both explain analyze-files to you off list?

Best regards,

Arjen

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