Re: Asynchronous Append on postgres_fdw nodes.

On 4/23/21 8:12 AM, Etsuro Fujita wrote:
> I have committed the patch.
Small mistake i found. If no tuple was received from a foreign 
partition, explain shows that we never executed node. For example,
if we have 0 tuples in f1 and 100 tuples in f2:

Query:
EXPLAIN (ANALYZE, VERBOSE, TIMING OFF, COSTS OFF)
SELECT * FROM (SELECT * FROM f1 UNION ALL SELECT * FROM f2) AS q1
LIMIT 101;

Explain:
  Limit (actual rows=100 loops=1)
    Output: f1.a
    ->  Append (actual rows=100 loops=1)
          ->  Async Foreign Scan on public.f1 (never executed)
                Output: f1.a
                Remote SQL: SELECT a FROM public.l1
          ->  Async Foreign Scan on public.f2 (actual rows=100 loops=1)
                Output: f2.a
                Remote SQL: SELECT a FROM public.l2

The patch in the attachment fixes this.

-- 
regards,
Andrey Lepikhov
Postgres Professional