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
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index e201b5404e..a960ada441 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -6857,8 +6857,13 @@ produce_tuple_asynchronously(AsyncRequest *areq, bool fetch)
}
else
{
- /* There's nothing more to do; just return a NULL pointer */
- result = NULL;
+ /*
+ * There's nothing more to do; just check it and get an empty slot
+ * from the child node.
+ */
+ result = ExecProcNode((PlanState *) node);
+ Assert(TupIsNull(result));
+
/* Mark the request as complete */
ExecAsyncRequestDone(areq, result);
}
