Re: explain analyze output with parallel workers - question aboutmeaning of information for explain.depesz.com

On Tue, Nov 28, 2017 at 2:23 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> That is wrong and I think you have hit a bug.  It should be 2974 * 5 =
> 14870 as you have seen in other cases.  The problem is that during
> rescan, we generally reinitialize the required state, but we forgot to
> reinitialize the instrumentation related memory which is used in the
> accumulation of stats, so changing that would fix some part of this
> problem which is that at Parallel node, you won't see wrong values.
> However, we also need to ensure that the per-worker details also get
> accumulated across rescans.  Attached patch should fix the problem you
> are seeing.  I think this needs some more analysis and testing to see
> if everything works in the desired way.
>
> Is it possible for you to test the attached patch and see if you are
> still seeing any unexpected values?

FWIW, this looks sensible to me.  Not sure if there's any good way to
write a regression test for it.

-- 
Robert Haas
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