Disallow collecting transition tuples from child foreign tables.

Commit 9e6104c66 disallowed transition tables on foreign tables, but
failed to account for cases where a foreign table is a child table of a
partitioned/inherited table on which transition tables exist, leading to
incorrect transition tuples collected from such foreign tables for
queries on the parent table triggering transition capture.  This
occurred not only for inherited UPDATE/DELETE but for partitioned INSERT
later supported by commit 3d956d956, which should have handled it at
least for the INSERT case, but didn't.

To fix, modify ExecAR*Triggers to throw an error if the given relation
is a foreign table requesting transition capture.  Also, this commit
fixes make_modifytable so that in case of an inherited UPDATE/DELETE
triggering transition capture, FDWs choose normal operations to modify
child foreign tables, not DirectModify; which is needed because they
would otherwise skip the calls to ExecAR*Triggers at execution, causing
unexpected behavior.

Author: Etsuro Fujita <etsuro.fujita@gmail.com>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CAPmGK14QJYikKzBDCe3jMbpGENnQ7popFmbEgm-XTNuk55oyHg%40mail.gmail.com
Backpatch-through: 13

src/backend/commands/trigger.c

@@ -2606,6 +2606,15 @@ ExecARInsertTriggers(EState *estate, ResultRelInfo *relinfo,
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 
+	if (relinfo->ri_FdwRoutine && transition_capture &&
+		transition_capture->tcs_insert_new_table)
+	{
+		Assert(relinfo->ri_RootResultRelInfo);
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot collect transition tuples from child foreign tables")));
+	}
+
 	if ((trigdesc && trigdesc->trig_insert_after_row) ||
 		(transition_capture && transition_capture->tcs_insert_new_table))
 		AfterTriggerSaveEvent(estate, relinfo, NULL, NULL,
@@ -2864,6 +2873,15 @@ ExecARDeleteTriggers(EState *estate,
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 
+	if (relinfo->ri_FdwRoutine && transition_capture &&
+		transition_capture->tcs_delete_old_table)
+	{
+		Assert(relinfo->ri_RootResultRelInfo);
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot collect transition tuples from child foreign tables")));
+	}
+
 	if ((trigdesc && trigdesc->trig_delete_after_row) ||
 		(transition_capture && transition_capture->tcs_delete_old_table))
 	{
@@ -3206,6 +3224,16 @@ ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 
+	if (relinfo->ri_FdwRoutine && transition_capture &&
+		(transition_capture->tcs_update_old_table ||
+		 transition_capture->tcs_update_new_table))
+	{
+		Assert(relinfo->ri_RootResultRelInfo);
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot collect transition tuples from child foreign tables")));
+	}
+
 	if ((trigdesc && trigdesc->trig_update_after_row) ||
 		(transition_capture &&
 		 (transition_capture->tcs_update_old_table ||

src/backend/optimizer/plan/createplan.c

@@ -6989,6 +6989,8 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 				 List *mergeActionLists, int epqParam)
 {
 	ModifyTable *node = makeNode(ModifyTable);
+	bool		transition_tables = false;
+	bool		transition_tables_valid = false;
 	List	   *fdw_private_list;
 	Bitmapset  *direct_modify_plans;
 	ListCell   *lc;
@@ -7134,7 +7136,7 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 		 * callback functions needed for that and (2) there are no local
 		 * structures that need to be run for each modified row: row-level
 		 * triggers on the foreign table, stored generated columns, WITH CHECK
-		 * OPTIONs from parent views.
+		 * OPTIONs from parent views, transition tables on the named relation.
 		 */
 		direct_modify = false;
 		if (fdwroutine != NULL &&
@@ -7145,7 +7147,19 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 			withCheckOptionLists == NIL &&
 			!has_row_triggers(root, rti, operation) &&
 			!has_stored_generated_columns(root, rti))
-			direct_modify = fdwroutine->PlanDirectModify(root, node, rti, i);
+		{
+			/* transition_tables is the same for all result relations */
+			if (!transition_tables_valid)
+			{
+				transition_tables = has_transition_tables(root,
+														  nominalRelation,
+														  operation);
+				transition_tables_valid = true;
+			}
+			if (!transition_tables)
+				direct_modify = fdwroutine->PlanDirectModify(root, node,
+															 rti, i);
+		}
 		if (direct_modify)
 			direct_modify_plans = bms_add_member(direct_modify_plans, i);
 

src/backend/optimizer/util/plancat.c

@@ -2217,6 +2217,60 @@ has_row_triggers(PlannerInfo *root, Index rti, CmdType event)
 	return result;
 }
 
+/*
+ * has_transition_tables
+ *
+ * Detect whether the specified relation has any transition tables for event.
+ */
+bool
+has_transition_tables(PlannerInfo *root, Index rti, CmdType event)
+{
+	RangeTblEntry *rte = planner_rt_fetch(rti, root);
+	Relation	relation;
+	TriggerDesc *trigDesc;
+	bool		result = false;
+
+	Assert(rte->rtekind == RTE_RELATION);
+
+	/* Currently foreign tables cannot have transition tables */
+	if (rte->relkind == RELKIND_FOREIGN_TABLE)
+		return result;
+
+	/* Assume we already have adequate lock */
+	relation = table_open(rte->relid, NoLock);
+
+	trigDesc = relation->trigdesc;
+	switch (event)
+	{
+		case CMD_INSERT:
+			if (trigDesc &&
+				trigDesc->trig_insert_new_table)
+				result = true;
+			break;
+		case CMD_UPDATE:
+			if (trigDesc &&
+				(trigDesc->trig_update_old_table ||
+				 trigDesc->trig_update_new_table))
+				result = true;
+			break;
+		case CMD_DELETE:
+			if (trigDesc &&
+				trigDesc->trig_delete_old_table)
+				result = true;
+			break;
+			/* There is no separate event for MERGE, only INSERT/UPDATE/DELETE */
+		case CMD_MERGE:
+			result = false;
+			break;
+		default:
+			elog(ERROR, "unrecognized CmdType: %d", (int) event);
+			break;
+	}
+
+	table_close(relation, NoLock);
+	return result;
+}
+
 /*
  * has_stored_generated_columns
  *