From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Onder Kalaci <onderk(at)microsoft(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Assertion failure with LEFT JOINs among >500 relations |
Date: | 2020-10-18 23:37:49 |
Message-ID: | CAApHDvps=BBWjDV89g8BnCe0XujuT1Mz2_UtMiFUZPXrEyUmsA@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, 19 Oct 2020 at 12:25, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > On Mon, 19 Oct 2020 at 12:10, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> TBH, I see no need to do anything in the back branches. This is not
> >> an issue for production usage.
>
> > I understand the Assert failure is pretty harmless, so non-assert
> > builds shouldn't suffer too greatly. I just assumed that any large
> > stakeholders invested in upgrading to a newer version of PostgreSQL
> > may like to run various tests with their application against an assert
> > enabled version of PostgreSQL perhaps to gain some confidence in the
> > upgrade. A failing assert is unlikely to inspire additional
> > confidence.
>
> If any existing outside regression tests hit such corner cases, then
> (a) we'd have heard about it, and (b) likely they'd fail in the older
> branch as well. So I don't buy the argument that this will dissuade
> somebody from upgrading.
hmm, well it was reported to us. Perhaps swapping the word "upgrading"
for "migrating".
It would be good to hear Onder's case to see if he has a good argument
for having a vested interest in pg13 not failing this way with assets
enabled.
> I do, on the other hand, buy the idea that if anyone is indeed working
> in this realm, they might be annoyed by a behavior change in a stable
> branch. So it cuts both ways. On balance I don't think we should
> touch this in the back branches.
I guess we could resolve that concern by just changing the failing
assert to become: Assert(outer_skip_rows <= outer_rows ||
isinf(outer_rows));
It's pretty grotty but should address that concern.
David
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