Record parents of triggers

This let us get rid of a recently introduced ugly hack (commit
1fa846f1).

Author: Álvaro Herrera
Reviewed-by: Amit Langote, Tom Lane
Discussion: https://postgr.es/m/20200217215641.GA29784@alvherre.pgsql

doc/src/sgml/catalogs.sgml

@@ -6951,6 +6951,17 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       <entry>The table this trigger is on</entry>
      </row>
 
+     <row>
+      <entry><structfield>tgparentid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry><literal><link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link>.oid</literal></entry>
+      <entry>
+       Parent trigger that this trigger is cloned from, zero if not a clone;
+       this happens when partitions are created or attached to a partitioned
+       table.
+      </entry>
+     </row>
+
      <row>
       <entry><structfield>tgname</structfield></entry>
       <entry><type>name</type></entry>

src/backend/commands/tablecmds.c

@@ -16447,54 +16447,6 @@ out:
 	MemoryContextDelete(cxt);
 }
 
-/*
- * isPartitionTrigger
- *		Subroutine for CloneRowTriggersToPartition: determine whether
- *		the given trigger has been cloned from another one.
- *
- * We use pg_depend as a proxy for this, since we don't have any direct
- * evidence.  This is an ugly hack to cope with a catalog deficiency.
- * Keep away from children.  Do not stare with naked eyes.  Do not propagate.
- */
-static bool
-isPartitionTrigger(Oid trigger_oid)
-{
-	Relation	pg_depend;
-	ScanKeyData key[2];
-	SysScanDesc scan;
-	HeapTuple	tup;
-	bool		found = false;
-
-	pg_depend = table_open(DependRelationId, AccessShareLock);
-
-	ScanKeyInit(&key[0], Anum_pg_depend_classid,
-				BTEqualStrategyNumber,
-				F_OIDEQ,
-				ObjectIdGetDatum(TriggerRelationId));
-	ScanKeyInit(&key[1], Anum_pg_depend_objid,
-				BTEqualStrategyNumber,
-				F_OIDEQ,
-				ObjectIdGetDatum(trigger_oid));
-
-	scan = systable_beginscan(pg_depend, DependDependerIndexId,
-							  true, NULL, 2, key);
-	while ((tup = systable_getnext(scan)) != NULL)
-	{
-		Form_pg_depend dep = (Form_pg_depend) GETSTRUCT(tup);
-
-		if (dep->refclassid == TriggerRelationId)
-		{
-			found = true;
-			break;
-		}
-	}
-
-	systable_endscan(scan);
-	table_close(pg_depend, AccessShareLock);
-
-	return found;
-}
-
 /*
  * CloneRowTriggersToPartition
  *		subroutine for ATExecAttachPartition/DefineRelation to create row
@@ -16537,11 +16489,10 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
 
 		/*
 		 * Internal triggers require careful examination.  Ideally, we don't
-		 * clone them.
-		 *
-		 * However, if our parent is a partitioned relation, there might be
-		 * internal triggers that need cloning.  In that case, we must skip
-		 * clone it if the trigger on parent depends on another trigger.
+		 * clone them.  However, if our parent is itself a partition, there
+		 * might be internal triggers that must not be skipped; for example,
+		 * triggers on our parent that are in turn clones from its parent (our
+		 * grandparent) are marked internal, yet they are to be cloned.
 		 *
 		 * Note we dare not verify that the other trigger belongs to an
 		 * ancestor relation of our parent, because that creates deadlock
@@ -16549,7 +16500,7 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
 		 */
 		if (trigForm->tgisinternal &&
 			(!parent->rd_rel->relispartition ||
-			 !isPartitionTrigger(trigForm->oid)))
+			 !OidIsValid(trigForm->tgparentid)))
 			continue;
 
 		/*

src/backend/commands/trigger.c

@@ -847,6 +847,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 
 	values[Anum_pg_trigger_oid - 1] = ObjectIdGetDatum(trigoid);
 	values[Anum_pg_trigger_tgrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
+	values[Anum_pg_trigger_tgparentid - 1] = ObjectIdGetDatum(parentTriggerOid);
 	values[Anum_pg_trigger_tgname - 1] = DirectFunctionCall1(namein,
 															 CStringGetDatum(trigname));
 	values[Anum_pg_trigger_tgfoid - 1] = ObjectIdGetDatum(funcoid);

src/include/catalog/pg_trigger.h

@@ -35,6 +35,7 @@ CATALOG(pg_trigger,2620,TriggerRelationId)
 {
 	Oid			oid;			/* oid */
 	Oid			tgrelid;		/* relation trigger is attached to */
+	Oid			tgparentid;		/* OID of parent trigger, if any */
 	NameData	tgname;			/* trigger's name */
 	Oid			tgfoid;			/* OID of function to be called */
 	int16		tgtype;			/* BEFORE/AFTER/INSTEAD, UPDATE/DELETE/INSERT,

src/test/regress/expected/sanity_check.out

@@ -208,6 +208,9 @@ timestamp_tbl|f
 timestamptz_tbl|f
 timetz_tbl|f
 tmp|f
+trigger_parted|t
+trigger_parted_p1|t
+trigger_parted_p1_1|t
 varchar_tbl|f
 view_base_table|t
 -- restore normal output mode

src/test/regress/expected/triggers.out

@@ -2928,3 +2928,12 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+-- Leave around some objects for other tests
+create table trigger_parted (a int primary key) partition by list (a);
+create function trigger_parted_trigfunc() returns trigger language plpgsql as
+  $$ begin end; $$;
+create trigger aft_row after insert or update on trigger_parted
+  for each row execute function trigger_parted_trigfunc();
+create table trigger_parted_p1 partition of trigger_parted for values in (1)
+  partition by list (a);
+create table trigger_parted_p1_1 partition of trigger_parted_p1 for values in (1);

src/test/regress/sql/triggers.sql

@@ -2213,3 +2213,13 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+
+-- Leave around some objects for other tests
+create table trigger_parted (a int primary key) partition by list (a);
+create function trigger_parted_trigfunc() returns trigger language plpgsql as
+  $$ begin end; $$;
+create trigger aft_row after insert or update on trigger_parted
+  for each row execute function trigger_parted_trigfunc();
+create table trigger_parted_p1 partition of trigger_parted for values in (1)
+  partition by list (a);
+create table trigger_parted_p1_1 partition of trigger_parted_p1 for values in (1);