Re: Avoiding hash join batch explosions with extreme skew and weird stats - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Avoiding hash join batch explosions with extreme skew and weird stats
Date
Msg-id 7554.1558047523@sss.pgh.pa.us
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In response to Re: Avoiding hash join batch explosions with extreme skew and weird stats  (Thomas Munro <thomas.munro@gmail.com>)
Responses Re: Avoiding hash join batch explosions with extreme skew and weirdstats  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
List pgsql-hackers
Thomas Munro <thomas.munro@gmail.com> writes:
> On Fri, May 17, 2019 at 4:39 AM Tomas Vondra
> <tomas.vondra@2ndquadrant.com> wrote:
>> I kinda like the idea with increasing the spaceAllowed value. Essentially,
>> if we decide adding batches would be pointless, increasing the memory
>> budget is the only thing we can do anyway.

> But that's not OK, we need to fix THAT.

I don't think it's necessarily a good idea to suppose that we MUST
fit in work_mem come what may.  It's likely impossible to guarantee
that in all cases.  Even if we can, a query that runs for eons will
help nobody.

            regards, tom lane



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