Re: parallelize queries containing subplans

On Tue, Jan 24, 2017 at 10:59 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> 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.
>>
>
> Yeah, actually setting parallel_safety information for subplan from
> corresponding is okay. However, in this particular case as we know
> that it might not be of any use till we enable parallelism for CTE
> Scan (and doing that is certainly not essential for this project).
> So, I have set parallel_safe as false for CTE subplans.
>

Moved this patch to next CF.

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