Commit 30a35bca authored by Tom Lane's avatar Tom Lane

Fix crash in postgres_fdw for provably-empty remote UPDATE/DELETE.

In 86dc9005, I'd written find_modifytable_subplan with the assumption
that if the immediate child of a ModifyTable is a Result, it must be
a projecting Result with a subplan.  However, if the UPDATE or DELETE
has a provably-constant-false WHERE clause, that's not so: we'll
generate a dummy subplan with a childless Result.  Add the missing
null-check so we don't crash on such cases.

Per report from Alexander Pyhalov.

Discussion: https://postgr.es/m/b9a6f53549456b2f3e2fd150dcd79d72@postgrespro.ru
parent e48f2afe
...@@ -6853,6 +6853,26 @@ DROP TRIGGER trig_row_before ON rem1; ...@@ -6853,6 +6853,26 @@ DROP TRIGGER trig_row_before ON rem1;
DROP TRIGGER trig_row_after ON rem1; DROP TRIGGER trig_row_after ON rem1;
DROP TRIGGER trig_local_before ON loc1; DROP TRIGGER trig_local_before ON loc1;
-- Test direct foreign table modification functionality -- Test direct foreign table modification functionality
EXPLAIN (verbose, costs off)
DELETE FROM rem1; -- can be pushed down
QUERY PLAN
---------------------------------------------
Delete on public.rem1
-> Foreign Delete on public.rem1
Remote SQL: DELETE FROM public.loc1
(3 rows)
EXPLAIN (verbose, costs off)
DELETE FROM rem1 WHERE false; -- currently can't be pushed down
QUERY PLAN
-------------------------------------------------------
Delete on public.rem1
Remote SQL: DELETE FROM public.loc1 WHERE ctid = $1
-> Result
Output: ctid
One-Time Filter: false
(5 rows)
-- Test with statement-level triggers -- Test with statement-level triggers
CREATE TRIGGER trig_stmt_before CREATE TRIGGER trig_stmt_before
BEFORE DELETE OR INSERT OR UPDATE ON rem1 BEFORE DELETE OR INSERT OR UPDATE ON rem1
......
...@@ -2370,7 +2370,9 @@ find_modifytable_subplan(PlannerInfo *root, ...@@ -2370,7 +2370,9 @@ find_modifytable_subplan(PlannerInfo *root,
if (subplan_index < list_length(appendplan->appendplans)) if (subplan_index < list_length(appendplan->appendplans))
subplan = (Plan *) list_nth(appendplan->appendplans, subplan_index); subplan = (Plan *) list_nth(appendplan->appendplans, subplan_index);
} }
else if (IsA(subplan, Result) && IsA(outerPlan(subplan), Append)) else if (IsA(subplan, Result) &&
outerPlan(subplan) != NULL &&
IsA(outerPlan(subplan), Append))
{ {
Append *appendplan = (Append *) outerPlan(subplan); Append *appendplan = (Append *) outerPlan(subplan);
......
...@@ -1738,6 +1738,10 @@ DROP TRIGGER trig_local_before ON loc1; ...@@ -1738,6 +1738,10 @@ DROP TRIGGER trig_local_before ON loc1;
-- Test direct foreign table modification functionality -- Test direct foreign table modification functionality
EXPLAIN (verbose, costs off)
DELETE FROM rem1; -- can be pushed down
EXPLAIN (verbose, costs off)
DELETE FROM rem1 WHERE false; -- currently can't be pushed down
-- Test with statement-level triggers -- Test with statement-level triggers
CREATE TRIGGER trig_stmt_before CREATE TRIGGER trig_stmt_before
......
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