From: | Thom Brown <thom(at)linux(dot)com> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel Seq Scan |
Date: | 2015-11-13 15:46:42 |
Message-ID: | CAA-aLv6OWR3GO35YEpEVULcmpYFYU52LPd5q1qs5i0CJ0xefag@mail.gmail.com |
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Lists: | pgsql-hackers |
On 13 November 2015 at 15:22, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Fri, Nov 13, 2015 at 7:59 PM, Thom Brown <thom(at)linux(dot)com> wrote:
>>
>> On 13 November 2015 at 13:38, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> > On Wed, Nov 11, 2015 at 11:40 PM, Pavel Stehule
>> > <pavel(dot)stehule(at)gmail(dot)com>
>> > wrote:
>> >>
>> >>
>> >> yes - the another little bit unclean in EXPLAIN is number of workers.
>> >> If I
>> >> understand to the behave, the query is processed by two processes if
>> >> workers
>> >> in the explain is one.
>> >>
>> >
>> > You are right and I think that is current working model of Gather
>> > node which seems okay. I think the more serious thing here
>> > is that there is possibility that Explain Analyze can show the
>> > number of workers as more than actual workers working for Gather
>> > node. We have already discussed that Explain Analyze should
>> > the actual number of workers used in query execution, patch for
>> > the same is still pending.
>>
>> This may have already been discussed before, but in a verbose output,
>> would it be possible to see the nodes for each worker?
>>
>
> There will be hardly any difference in nodes for each worker and it could
> be very long plan for large number of workers. What kind of additional
> information you want which can't be shown in current format.
For explain plans, not that useful, but it's useful to see how long
each worker took for explain analyse. And I imagine as more
functionality is added to scan partitions and foreign scans, it will
perhaps be more useful when the plans won't be identical. (or would
they?)
>>
>> And perhaps associated PIDs?
>>
>
> Yeah, that can be useful, if others also feel like it is important, I can
> look into preparing a patch for the same.
Thanks.
Thom
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