Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3 - Mailing list pgsql-general

From Greg Stark
Subject Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3
Date
Msg-id 87lm0mpwo2.fsf@stark.dyndns.tv
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In response to Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3
List pgsql-general
Tom Lane <tgl@sss.pgh.pa.us> writes:

> Greg Stark <gsstark@mit.edu> writes:
>
> The estimated row counts for the bottom-level scans show some
> differences, which probably account for the differing choice of plans.
>
> Are these actually the same data with up-to-date ANALYZE stats in both
> cases?  I do not recall that we've made any adjustments to the basic
> statistical estimation routines since 7.3 ...

The exact same data. I just copied the data using pg_dumpall to do the upgrade
and haven't updated either database at all since. The analyze stats should be
pretty up-to-date but in any case should be the same for both assuming they
get copied in the dump as well.

--
greg

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