Re: parallel query hangs - impossible to cancel - Mailing list pgsql-bugs

From Thomas Munro
Subject Re: parallel query hangs - impossible to cancel
Date
Msg-id CA+hUKGL+JUk6pADTCkJaaVaZct0Kcd7GKaE8y3GwihVy1eH+fQ@mail.gmail.com
Whole thread Raw
In response to Re: parallel query hangs - impossible to cancel  (Floris Van Nee <florisvannee@Optiver.com>)
List pgsql-bugs
On Tue, Mar 26, 2019 at 2:17 AM Floris Van Nee <florisvannee@optiver.com> wrote:
> Thank you! I indeed saw another thread that looked like it, but I wasn't aware that the problem had been fixed
already.This indeed seems similar to my stack trace.
 

Hi Floris,

I should probably highlight something that is buried in one of those
long threads Sergei posted: until the fix is released, the simplest
workaround is to disable parallel query with SET
max_parallel_workers_per_gather = 0 if you're affected by the bug.  In
theory you could also make it vanishingly rare by finding a way to
call srandom(getpid()) in every forked process with an extension.
It's a rare timing bug, but some workloads seem to be more prone to
it, so unfortunately it went undetected for a long time.

-- 
Thomas Munro
https://enterprisedb.com


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