Re: crashes due to setting max_parallel_workers=0

On Sat, Mar 25, 2017 at 6:31 PM, David Rowley
<david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> On 25 March 2017 at 23:09, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com> wrote:
>> Also another point which I think we should fix is, when someone set
>> max_parallel_workers = 0, we should also set the
>> max_parallel_workers_per_gather
>> to zero. So that way it we can avoid generating the gather path with
>> max_parallel_worker = 0.
>
> I see that it was actually quite useful that it works the way it does.
> If it had worked the same as max_parallel_workers_per_gather, then
> likely Tomas would never have found this bug.
>
> I wondered if there's anything we can do here to better test cases
> when no workers are able to try to ensure the parallel nodes work
> correctly, but the more I think about it, the more I don't see wrong
> with just using SET max_parallel_workers = 0;
>
> My vote would be to leave the GUC behaviour as is and add some tests
> to select_parallel.sql which exploit setting max_parallel_workers to 0
> for running some tests.
>

I think force_parallel_mode=regress should test the same thing.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com