Prohibit renaming child trigger on distributed partition pre PG15 (#6290)

Pre PG15, renaming child triggers on partitions is allowed. When
creating a trigger in a distributed parent partitioned table, the
triggers on the shards of the partitions have the same name with
the triggers on the corresponding parent shards of the parent
table. Therefore, they don't have the same appended shard id as
the shard id of the partition. Hence, when trying to rename a
child trigger on a partition of a distributed table, we can't
correctly find the triggers on the shards of the partition in
order to rename them since we append a different shard id to the
name of the trigger. Since we can't find the trigger we get a
misleading error of inexistent trigger.

In this commit we prohibit renaming child triggers on distributed
partitions altogether.

src/backend/distributed/commands/distribute_object_ops.c

@@ -1176,7 +1176,7 @@ static DistributeObjectOps View_Rename = {
 static DistributeObjectOps Trigger_Rename = {
 	.deparse = NULL,
 	.qualify = NULL,
-	.preprocess = NULL,
+	.preprocess = PreprocessAlterTriggerRenameStmt,
 	.operationType = DIST_OPS_ALTER,
 	.postprocess = PostprocessAlterTriggerRenameStmt,
 	.address = NULL,

src/backend/distributed/commands/trigger.c

@@ -53,6 +53,9 @@ static void ExtractDropStmtTriggerAndRelationName(DropStmt *dropTriggerStmt,
 												  char **relationName);
 static void ErrorIfDropStmtDropsMultipleTriggers(DropStmt *dropTriggerStmt);
 static int16 GetTriggerTypeById(Oid triggerId);
+#if (PG_VERSION_NUM < PG_VERSION_15)
+static void ErrorOutIfCloneTrigger(Oid tgrelid, const char *tgname);
+#endif
 
 
 /* GUC that overrides trigger checks for distributed tables and reference tables */
@@ -319,6 +322,40 @@ CreateTriggerEventExtendNames(CreateTrigStmt *createTriggerStmt, char *schemaNam
 }
 
 
+/*
+ * PreprocessAlterTriggerRenameStmt is called before a ALTER TRIGGER RENAME
+ * command has been executed by standard process utility. This function errors
+ * out if we are trying to rename a child trigger on a partition of a distributed
+ * table. In PG15, this is not allowed anyway.
+ */
+List *
+PreprocessAlterTriggerRenameStmt(Node *node, const char *queryString,
+								 ProcessUtilityContext processUtilityContext)
+{
+#if (PG_VERSION_NUM < PG_VERSION_15)
+	RenameStmt *renameTriggerStmt = castNode(RenameStmt, node);
+	Assert(renameTriggerStmt->renameType == OBJECT_TRIGGER);
+
+	RangeVar *relation = renameTriggerStmt->relation;
+
+	bool missingOk = false;
+	Oid relationId = RangeVarGetRelid(relation, ALTER_TRIGGER_LOCK_MODE, missingOk);
+
+	if (!IsCitusTable(relationId))
+	{
+		return NIL;
+	}
+
+	EnsureCoordinator();
+	ErrorOutForTriggerIfNotSupported(relationId);
+
+	ErrorOutIfCloneTrigger(relationId, renameTriggerStmt->subname);
+#endif
+
+	return NIL;
+}
+
+
 /*
  * PostprocessAlterTriggerRenameStmt is called after a ALTER TRIGGER RENAME
  * command has been executed by standard process utility. This function errors
@@ -611,6 +648,64 @@ ErrorOutForTriggerIfNotSupported(Oid relationId)
 }
 
 
+#if (PG_VERSION_NUM < PG_VERSION_15)
+
+/*
+ * ErrorOutIfCloneTrigger is a helper function to error
+ * out if we are trying to rename a child trigger on a
+ * partition of a distributed table.
+ * A lot of this code is borrowed from PG15 because
+ * renaming clone triggers isn't allowed in PG15 anymore.
+ */
+static void
+ErrorOutIfCloneTrigger(Oid tgrelid, const char *tgname)
+{
+	HeapTuple tuple;
+	ScanKeyData key[2];
+
+	Relation tgrel = table_open(TriggerRelationId, RowExclusiveLock);
+
+	/*
+	 * Search for the trigger to modify.
+	 */
+	ScanKeyInit(&key[0],
+				Anum_pg_trigger_tgrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(tgrelid));
+	ScanKeyInit(&key[1],
+				Anum_pg_trigger_tgname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				CStringGetDatum(tgname));
+	SysScanDesc tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
+											NULL, 2, key);
+
+	if (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
+	{
+		Form_pg_trigger trigform = (Form_pg_trigger) GETSTRUCT(tuple);
+
+		/*
+		 * If the trigger descends from a trigger on a parent partitioned
+		 * table, reject the rename.
+		 * Appended shard ids to find the trigger on the partition's shards
+		 * are not correct. Hence we would fail to find the trigger on the
+		 * partition's shard.
+		 */
+		if (OidIsValid(trigform->tgparentid))
+		{
+			ereport(ERROR, (
+						errmsg(
+							"cannot rename child triggers on distributed partitions")));
+		}
+	}
+
+	systable_endscan(tgscan);
+	table_close(tgrel, RowExclusiveLock);
+}
+
+
+#endif
+
+
 /*
  * GetDropTriggerStmtRelation takes a DropStmt for a trigger object and returns
  * RangeVar for the relation that owns the trigger.

src/include/distributed/commands.h

@@ -667,6 +667,8 @@ extern List * CreateTriggerStmtObjectAddress(Node *node, bool missingOk, bool
 											 isPostprocess);
 extern void CreateTriggerEventExtendNames(CreateTrigStmt *createTriggerStmt,
 										  char *schemaName, uint64 shardId);
+extern List * PreprocessAlterTriggerRenameStmt(Node *node, const char *queryString,
+											   ProcessUtilityContext processUtilityContext);
 extern List * PostprocessAlterTriggerRenameStmt(Node *node, const char *queryString);
 extern void AlterTriggerRenameEventExtendNames(RenameStmt *renameTriggerStmt,
 											   char *schemaName, uint64 shardId);

src/test/regress/expected/upgrade_distributed_triggers_before.out

@@ -241,3 +241,6 @@ SELECT * FROM sale_triggers ORDER BY 1, 2;
  truncate_trigger_xxxxxxx      | sale_california | O
 (12 rows)
 
+-- check that we can't rename child triggers on partitions of distributed tables
+ALTER TRIGGER another_trigger ON sale_newyork RENAME TO another_renamed_trigger;
+ERROR:  cannot rename child triggers on distributed partitions

src/test/regress/sql/upgrade_distributed_triggers_before.sql

@@ -114,3 +114,6 @@ FOR EACH ROW EXECUTE FUNCTION upgrade_distributed_triggers.record_sale();
 
 ALTER TRIGGER another_trigger ON sale RENAME TO another_renamed_trigger;
 SELECT * FROM sale_triggers ORDER BY 1, 2;
+
+-- check that we can't rename child triggers on partitions of distributed tables
+ALTER TRIGGER another_trigger ON sale_newyork RENAME TO another_renamed_trigger;