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 87adh2pr46.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>)
List pgsql-general
Tom Lane <tgl@sss.pgh.pa.us> writes:

> You could probably persuade it that hashed aggregation will be okay by
> increasing sort_mem sufficiently.  But it would also be interesting to
> see if the number-of-groups estimate can be improved ... 15122 is rather
> badly off from the true value of 31 ...

My sort_mem is already quite large, 53M. I think that's large enough even for
15,122 rows.


--
greg

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