Buffer pool statistics in Explain Analyze

Hi,

I believe it makes sense adding some more details to explain analyze output
like the number of pages read/written.
This will allow one to understand the workload the query puts on the server
making it easier to tune queries, choose the best indices, etc.

As far as I understand, this patch is rather trivial as
backend\storage\buffer collects the required information. The only thing is
to add several fields to the struct Instrumentation
(include\executor\instrument.h), fill them in during Instr* calls in
(backend\executor\instrument.c) and update backend\commands\explain.c to
report the collected data.

I think think this change is going to split page access statistics by each
and every execution node (much like 'actual time' is split now).

Will this patch ever be accepted?

Regards,
Vladimir Sitnikov