Re: Asynchronous Append on postgres_fdw nodes.

Hi,
I want to suggest one more improvement. Currently the
is_async_capable_path() routine allow only ForeignPath nodes as async 
capable path. But in some cases we can allow SubqueryScanPath as async 
capable too.

For example:
SELECT * FROM ((SELECT * FROM foreign_1)
UNION ALL
(SELECT a FROM foreign_2)) AS b;

is async capable, but:

SELECT * FROM ((SELECT * FROM foreign_1 LIMIT 10)
UNION ALL
(SELECT a FROM foreign_2 LIMIT 10)) AS b;

doesn't async capable.

The patch in attachment tries to improve this situation.

-- 
regards,
Andrey Lepikhov
Postgres Professional