Re: parallelize queries containing subplans

On Thu, Jan 19, 2017 at 4:51 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> On Thu, Jan 19, 2017 at 3:05 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>> During debugging I found that subplan created for below part of the
>> query is parallel_unsafe, Is it a problem or there is some explanation
>> of why it's not parallel_safe,
>
> Okay, so basically we don't have any mechanism to perform parallel
> scan on CTE. And, IMHO subplan built for CTE (using SS_process_ctes)
> must come along with CTE scan. So I think we can avoid setting below
> code because we will never be able to test its side effect, another
> argument can be that if we don't consider the final effect, and just
> see this subplan then by logic it should be marked parallel-safe or
> unsafe as per it's path and it will not have any side effect, as it
> will finally become parallel-unsafe. So it's your call to keep it
> either way.
Oops, you're right. We don't consider parallelism for RTE_CTE type.

--
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com