Re: [HACKERS] parallelize queries containing subplans

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От Kuntal Ghosh
Тема Re: [HACKERS] parallelize queries containing subplans
Дата
Msg-id CAGz5QCLZL+PsYdxVZ2BRMQxB=48Xk1-R83D3YpnbvebhvATa=g@mail.gmail.com
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Ответ на Re: [HACKERS] parallelize queries containing subplans  (Dilip Kumar <dilipbalaut@gmail.com>)
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On Thu, Jan 19, 2017 at 4:51 PM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Thu, Jan 19, 2017 at 3:05 PM, Dilip Kumar <dilipbalaut@gmail.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



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