Re: Default setting for enable_hashagg_disk - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Default setting for enable_hashagg_disk
Date
Msg-id 2217145.1593024050@sss.pgh.pa.us
Whole thread Raw
In response to Re: Default setting for enable_hashagg_disk  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Responses Re: Default setting for enable_hashagg_disk  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On Wed, Jun 24, 2020 at 01:29:56PM -0400, Tom Lane wrote:
>> If we feel we need something to let people have the v12 behavior
>> back, let's have
>> (1) enable_hashagg on/off --- controls planner, same as it ever was
>> (2) enable_hashagg_spill on/off --- controls executor by disabling spill

> What if a user specifies
>    enable_hashagg = on
>    enable_hashagg_spill = off

It would probably be reasonable for the planner to behave as it did
pre-v13, that is not choose hashagg if it estimates that work_mem
would be exceeded.  (So, okay, that means enable_hashagg_spill
affects both planner and executor ... but ISTM it's just one
behavior not two.)

            regards, tom lane



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