From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
---|---|
To: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: parallelize queries containing subplans |
Date: | 2017-01-24 09:46:16 |
Message-ID: | CAA4eK1+TqMziczzBUf0X2x3vTctTguu_QdfzRgjyQ_+o8PB-Xw@mail.gmail.com |
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Lists: | pgsql-hackers |
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.
>
missed the word *path* in above sentence.
/corresponding/corresponding path
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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