Re: Fix incorrect start up costs for WindowAgg paths (bug #17862) - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Fix incorrect start up costs for WindowAgg paths (bug #17862)
Date
Msg-id 3551059.1691110006@sss.pgh.pa.us
Whole thread Raw
In response to Re: Fix incorrect start up costs for WindowAgg paths (bug #17862)  (Nathan Bossart <nathandbossart@gmail.com>)
List pgsql-hackers
Nathan Bossart <nathandbossart@gmail.com> writes:
> On Fri, Aug 04, 2023 at 09:28:51AM +1200, David Rowley wrote:
>> Thank you for reviewing.  I've pushed the patch to master only.

> I'm seeing some reliable test failures for 32-bit builds on cfbot [0].  At
> a glance, it looks like the relations are swapped in the plan.

Yeah, I got the same result in a 32-bit FreeBSD VM.  Probably, the two
plans are of effectively-identical estimated cost, and there's some
roundoff effect in those estimates that differs between machines with
4-byte and 8-byte MAXALIGN.

You could likely stabilize the plan choice by joining two tables that
aren't of identical size -- maybe add an additional WHERE constraint
on one of the tables?

            regards, tom lane



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