Re: parallel query hangs - impossible to cancel

On Tue, Mar 26, 2019 at 2:17 AM Floris Van Nee <florisvannee(at)optiver(dot)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