Re: Parallel Seq Scan

On 13 November 2015 at 15:22, Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Fri, Nov 13, 2015 at 7:59 PM, Thom Brown <thom@linux.com> wrote:
>>
>> On 13 November 2015 at 13:38, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> > On Wed, Nov 11, 2015 at 11:40 PM, Pavel Stehule
>> > <pavel.stehule@gmail.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