Re: Explain buffers wrong counter with parallel plans

On 04/29/2018 05:10 PM, Amit Kapila wrote:
> Yeah, it would have been convenient, if Gather and Finalize Aggregate
> displays that way as it would have been easier for users to
> understand.  However, as of now, the aggregated stats for parallel
> workers and leader are displayed at parallel/partial nodes as is
> displayed in the plan.  So according to me, what you are seeing is
> okay, it is only slightly tricky to understand it.
>
[...]
>
>> I played with git bisect and I found this commit :
>>
>> commit 01edb5c7fc3bcf6aea15f2b3be36189b52ad9d1a
>> Author: Tom Lane <tgl@sss.pgh.pa.us>
>> Date:   Fri Sep 1 17:38:54 2017 -0400
>>
> I think you were seeing different results before this commit because
> before that we were shutting down workers as soon as parallel workers
> are done and the buffer_usage stats were accumulated and were being
> used for upper nodes.  According to me behavior after the commit is
> consistent, for example, I think if you check the case of GatherMerge
> before this commit, you will still get the stats in the way it is
> after commit.

I understand. Maybe, this change should be mentioned in releases notes and/or
documentation?

Thanks,