| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
| Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tim Palmer <tim3sp(at)gmail(dot)com> |
| Subject: | Re: Fix incorrect start up costs for WindowAgg paths (bug #17862) |
| Date: | 2023-08-04 00:46:46 |
| Message-ID: | 3551059.1691110006@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Nathan Bossart <nathandbossart(at)gmail(dot)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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