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Re: Additional size of hash table is alway zero for hash aggregates - Mailing list pgsql-hackers

From Pengzhou Tang
Subject Re: Additional size of hash table is alway zero for hash aggregates
Date
Msg-id CAG4reASZc61PzNUd0p3qgrAgYpZtNxwHhcXipzUjQdhcJ2iaOA@mail.gmail.com
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In response to Re: Additional size of hash table is alway zero for hash aggregates  (Andres Freund <andres@anarazel.de>)
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Thanks, Andres Freund and Andres Gierth.

To be related, can I invite you to help to review the parallel grouping sets
patches? It will be very great to hear some comments from you since you
contributed most of the codes for grouping sets.


Thanks,
Pengzhou

On Fri, Mar 13, 2020 at 3:16 AM Andres Freund <andres@anarazel.de> wrote:
Hi,


On 2020-03-12 16:35:15 +0800, Pengzhou Tang wrote:
> When reading the grouping sets codes, I find that the additional size of
> the hash table for hash aggregates is always zero, this seems to be
> incorrect to me, attached a patch to fix it, please help to check.

Indeed, that's incorrect. Causes the number of buckets for the hashtable
to be set higher - the size is just used for that.  I'm a bit wary of
changing this in the stable branches - could cause performance changes?

Greetings,

Andres Freund

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