Horton

Re: Assertion failure with barriers in parallel hash join

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-10-12T23:18:11Z
Lists: pgsql-hackers 
On Tue, Oct 13, 2020 at 12:15 PM Melanie Plageman
<melanieplageman@gmail.com> wrote:
> On Thu, Oct 1, 2020 at 8:08 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>> On Tue, Sep 29, 2020 at 9:12 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>> Here's a throw-away patch to add some sleeps that trigger the problem,
>> and a first draft fix.  I'll do some more testing of this next week
>> and see if I can simplify it.
>
> I was just taking a look at the patch and noticed the commit message
> says:
>
> > With unlucky timing and parallel_leader_participation off...
>
> Is parallel_leader_participation being off required to reproduce the
> issue?

Yeah, because otherwise the leader detaches last so the problem doesn't arise.

Commits

  1. Fix race in parallel hash join batch cleanup, take II.

  2. Revert "Fix race in Parallel Hash Join batch cleanup."

  3. Fix race in Parallel Hash Join batch cleanup.

  4. Mop-up for wait event naming issues.