Re: 8.2rc1 (much) slower than 8.2dev? - Mailing list pgsql-performance

From Arjen van der Meijden
Subject Re: 8.2rc1 (much) slower than 8.2dev?
Date
Msg-id 45744FAA.20603@tweakers.net
Whole thread Raw
In response to Re: 8.2rc1 (much) slower than 8.2dev?  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: 8.2rc1 (much) slower than 8.2dev?  ("Jim C. Nasby" <jim@nasby.net>)
List pgsql-performance
Tom Lane wrote:
> Arjen van der Meijden <acmmailing@tweakers.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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