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

1 files changed, 54 insertions, 0 deletions

diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index c6a58afc5e5..6ce4efea118 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -2389,6 +2389,60 @@ has_row_triggers(PlannerInfo *root, Index rti, CmdType event)
 }
 
 /*
+ * 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
  *
  * Does table identified by RTI have any STORED GENERATED columns?