fix-problem-with-transition-tables-wip.patch

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 67f8e70f9c1..ee5f27d92e4 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -2544,6 +2544,15 @@ 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,
@@ -2787,6 +2796,15 @@ 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))
 	{
@@ -3115,6 +3133,16 @@ 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 ||
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 0b61aef962c..b4770fa632d 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -7174,6 +7174,8 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 	ModifyTable *node = makeNode(ModifyTable);
 	bool		returning_old_or_new = false;
 	bool		returning_old_or_new_valid = false;
+	bool		transition_tables = false;
+	bool		transition_tables_valid = false;
 	List	   *fdw_private_list;
 	Bitmapset  *direct_modify_plans;
 	ListCell   *lc;
@@ -7320,8 +7322,8 @@ 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, or Vars returning OLD/NEW in the
-		 * RETURNING list.
+		 * OPTIONs from parent views, transition tables on the named relation,
+		 * or Vars returning OLD/NEW in the RETURNING list.
 		 */
 		direct_modify = false;
 		if (fdwroutine != NULL &&
@@ -7333,7 +7335,10 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 			!has_row_triggers(root, rti, operation) &&
 			!has_stored_generated_columns(root, rti))
 		{
-			/* returning_old_or_new is the same for all result relations */
+			/*
+			 * returning_old_or_new and transition_tables are the same for all
+			 * result relations, respectively
+			 */
 			if (!returning_old_or_new_valid)
 			{
 				returning_old_or_new =
@@ -7342,7 +7347,18 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 				returning_old_or_new_valid = true;
 			}
 			if (!returning_old_or_new)
-				direct_modify = fdwroutine->PlanDirectModify(root, node, rti, i);
+			{
+				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);
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 59233b64730..dcba4b72198 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -2303,6 +2303,58 @@ 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;
+
+	if (rte->rtekind == RTE_RELATION &&
+		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
  *
diff --git a/src/include/optimizer/plancat.h b/src/include/optimizer/plancat.h
index cd74e4b1e8b..ac80458467b 100644
--- a/src/include/optimizer/plancat.h
+++ b/src/include/optimizer/plancat.h
@@ -72,6 +72,8 @@ extern double get_function_rows(PlannerInfo *root, Oid funcid, Node *node);
 
 extern bool has_row_triggers(PlannerInfo *root, Index rti, CmdType event);
 
+extern bool has_transition_tables(PlannerInfo *root, Index rti, CmdType event);
+
 extern bool has_stored_generated_columns(PlannerInfo *root, Index rti);
 
 extern Bitmapset *get_dependent_generated_columns(PlannerInfo *root, Index rti,