How do I track stats on foreign table access through foreign data wrapper?

Hi,

I'm using a foreign data wrapper to access mongodb and I'm looking for a
way to monitor query stats against foreign tables.

It looks like the common methods have limited support for foreign tables at
this time. pg_stat_statements collects the query, total time, and rows
returned, which is useful. But all the disk access stats are zero
(understandably). Looks like pg_stat_all_tables doesn't have any info on
foreign tables from my tests.

I'm interested in the following:

- Foreign table rows read
- Foreign table bytes read
- Foreign table read time

I'm working with my own fork of the FDW, so I could build these in myself,
but I was wondering if there's more generic support for this sort of stuff.
Or at the least, if I do implement it can I push it into another stats
collection framework rather than logging it.

Thanks,
David Crawford