Re: Oddity with parallel safety test for scan/join target in grouping_planner

(2019/03/11 14:14), Tom Lane wrote:
> Etsuro Fujita<fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
>> (2019/03/11 13:06), Tom Lane wrote:
>>> Is that the only possible outcome? Per Robert's summary quoted above,
>>> it seems like it might be possible for the code to decide that the final
>>> scan/join target to be parallel safe when it is not, leading to outright
>>> wrong answers or query failures.
>
>> Maybe I'm missing something, but I think that if the final scan/join
>> target is not parallel-safe, then the grouping target would not be
>> parallel-safe either, by the construction of the two targets, so I don't
>> think that we have such a correctness issue.
>
> Seems to me it's the other way around: the final target would include
> all functions invoked in the grouping target plus maybe some more.
> So a non-parallel-safe grouping target implies a non-parallel-safe
> final target, but not vice versa.

I mean the final *scan/join* target, not the final target.

Best regards,
Etsuro Fujita