Re: Assertion failure with barriers in parallel hash join

From: David Geier <geidav(dot)pg(at)gmail(dot)com>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Melanie Plageman <melanieplageman(at)gmail(dot)com>
Subject: Re: Assertion failure with barriers in parallel hash join
Date: 2022-06-06 15:01:23
Message-ID: CAPsAnrmTbUMnqzUBCBWvRa=V6nOeStT20b114CJ0eARfe4gWGg@mail.gmail.com
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Hi Thomas,

Correct. We're running with disabled parallel leader participation and we
have to do so, because another custom plan node we built relies on that.
That would be great. Anything else I can help with to get this patch in?

Thanks!

--
David
(ServiceNow)

On Fri, 3 Jun 2022 at 00:06, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:

> On Thu, Jun 2, 2022 at 9:31 PM David Geier <geidav(dot)pg(at)gmail(dot)com> wrote:
> > We recently encountered the same bug in the field. Oleksii Kozlov
> managed to come up with reproduction steps, which reliably trigger it.
> Interestingly, the bug does not only manifest as failing assertion, but
> also as segmentation fault; in builds with disabled and with enabled (!)
> assertions. So it can crash production environments. We applied the
> proposed patch v3 from Melanie to the REL_14_3 branch and can confirm that
> with the patch neither the assertion nor the segmentation fault still occur.
>
> Thanks for the report, testing, and for creating the CF entry.
>
> I assume you are using parallel_leader_participation=off, and the
> reason we haven't heard more about this is because few people do that.
> By coincidence I was just about to restart a bunch of hash join
> projects and have been paging the topic area back into my brain, so
> I'll start with another round of testing/analysis of this bug/patch
> next week.
>

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