Re: EXPLAIN VERBOSE with parallel Aggregate

On Sun, Apr 17, 2016 at 10:22:24AM -0400, Tom Lane wrote:
> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> > On 16 April 2016 at 04:27, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> +1 for the latter, if we can do it conveniently. I think exposing
> >> the names of the aggregate implementation functions would be very
> >> user-unfriendly, as nobody but us hackers knows what those are.
>
> > It does not really seem all that convenient to do this. It also seems
> > a bit strange to me to have a parent node report a column which does
> > not exist in any nodes descending from it. Remember that the combine
> > Aggref does not have the same ->args as its corresponding partial
> > Aggref. It's not all that clear to me if there is any nice way to do
> > have this work the way you'd like. If we were to just call
> > get_rule_expr() on the first arg of the combine aggregate node, it
> > would re-print the PARTIAL keyword again.
>
> This suggests to me that the parsetree representation for partial
> aggregates was badly chosen. If EXPLAIN can't recognize them, then
> neither can anything else, and we may soon find needs for telling
> the difference that are not just cosmetic. Maybe we need more
> fields in Aggref.

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The above-described topic is currently a PostgreSQL 9.6 open item. Robert,
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