Classify DROP operations by whether or not they are user-initiated.

This doesn't do anything useful just yet, but is intended as supporting
infrastructure for allowing sepgsql to sensibly check DROP permissions.

KaiGai Kohei and Robert Haas

src/backend/catalog/aclchk.c

@@ -1211,7 +1211,7 @@ SetDefaultACL(InternalDefaultACL *iacls)
 			myself.objectId = HeapTupleGetOid(tuple);
 			myself.objectSubId = 0;
 
-			performDeletion(&myself, DROP_RESTRICT);
+			performDeletion(&myself, DROP_RESTRICT, 0);
 		}
 	}
 	else

src/backend/catalog/dependency.c

@@ -171,7 +171,8 @@ static void reportDependentObjects(const ObjectAddresses *targetObjects,
 					   DropBehavior behavior,
 					   int msglevel,
 					   const ObjectAddress *origObject);
-static void deleteOneObject(const ObjectAddress *object, Relation depRel);
+static void deleteOneObject(const ObjectAddress *object,
+							Relation depRel, int32 flags);
 static void doDeletion(const ObjectAddress *object);
 static void AcquireDeletionLock(const ObjectAddress *object);
 static void ReleaseDeletionLock(const ObjectAddress *object);
@@ -205,10 +206,17 @@ static void getOpFamilyDescription(StringInfo buffer, Oid opfid);
  * that can participate in dependencies.  Note that the next two routines
  * are variants on the same theme; if you change anything here you'll likely
  * need to fix them too.
+ *
+ * flags should include PERFORM_DELETION_INTERNAL when the drop operation is
+ * not the direct result of a user-initiated action.  For example, when a
+ * temporary schema is cleaned out so that a new backend can use it, or when
+ * a column default is dropped as an intermediate step while adding a new one,
+ * that's an internal operation.  On the other hand, when the we drop something
+ * because the user issued a DROP statement against it, that's not internal.
  */
 void
 performDeletion(const ObjectAddress *object,
-				DropBehavior behavior)
+				DropBehavior behavior, int flags)
 {
 	Relation	depRel;
 	ObjectAddresses *targetObjects;
@@ -254,7 +262,7 @@ performDeletion(const ObjectAddress *object,
 	{
 		ObjectAddress *thisobj = targetObjects->refs + i;
 
-		deleteOneObject(thisobj, depRel);
+		deleteOneObject(thisobj, depRel, flags);
 	}
 
 	/* And clean up */
@@ -274,7 +282,7 @@ performDeletion(const ObjectAddress *object,
  */
 void
 performMultipleDeletions(const ObjectAddresses *objects,
-						 DropBehavior behavior)
+						 DropBehavior behavior, int flags)
 {
 	Relation	depRel;
 	ObjectAddresses *targetObjects;
@@ -336,7 +344,7 @@ performMultipleDeletions(const ObjectAddresses *objects,
 	{
 		ObjectAddress *thisobj = targetObjects->refs + i;
 
-		deleteOneObject(thisobj, depRel);
+		deleteOneObject(thisobj, depRel, flags);
 	}
 
 	/* And clean up */
@@ -407,7 +415,14 @@ deleteWhatDependsOn(const ObjectAddress *object,
 		if (thisextra->flags & DEPFLAG_ORIGINAL)
 			continue;
 
-		deleteOneObject(thisobj, depRel);
+		/*
+		 * Since this function is currently only used to clean out temporary
+		 * schemas, we pass PERFORM_DELETION_INTERNAL here, indicating that
+		 * the operation is an automatic system operation rather than a user
+		 * action.  If, in the future, this function is used for other
+		 * purposes, we might need to revisit this.
+		 */
+		deleteOneObject(thisobj, depRel, PERFORM_DELETION_INTERNAL);
 	}
 
 	/* And clean up */
@@ -950,7 +965,7 @@ reportDependentObjects(const ObjectAddresses *targetObjects,
  * depRel is the already-open pg_depend relation.
  */
 static void
-deleteOneObject(const ObjectAddress *object, Relation depRel)
+deleteOneObject(const ObjectAddress *object, Relation depRel, int flags)
 {
 	ScanKeyData key[3];
 	int			nkeys;

src/backend/catalog/heap.c

@@ -1528,7 +1528,7 @@ RemoveAttributeById(Oid relid, AttrNumber attnum)
  */
 void
 RemoveAttrDefault(Oid relid, AttrNumber attnum,
-				  DropBehavior behavior, bool complain)
+				  DropBehavior behavior, bool complain, bool internal)
 {
 	Relation	attrdef_rel;
 	ScanKeyData scankeys[2];
@@ -1559,7 +1559,8 @@ RemoveAttrDefault(Oid relid, AttrNumber attnum,
 		object.objectId = HeapTupleGetOid(tuple);
 		object.objectSubId = 0;
 
-		performDeletion(&object, behavior);
+		performDeletion(&object, behavior,
+						internal ? PERFORM_DELETION_INTERNAL : 0);
 
 		found = true;
 	}

src/backend/catalog/pg_shdepend.c

@@ -1240,7 +1240,7 @@ shdepDropOwned(List *roleids, DropBehavior behavior)
 	}
 
 	/* the dependency mechanism does the actual work */
-	performMultipleDeletions(deleteobjs, behavior);
+	performMultipleDeletions(deleteobjs, behavior, 0);
 
 	heap_close(sdepRel, RowExclusiveLock);
 

src/backend/commands/cluster.c

@@ -1443,7 +1443,7 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 	 * The new relation is local to our transaction and we know nothing
 	 * depends on it, so DROP_RESTRICT should be OK.
 	 */
-	performDeletion(&object, DROP_RESTRICT);
+	performDeletion(&object, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
 
 	/* performDeletion does CommandCounterIncrement at end */
 

src/backend/commands/dropcmds.c

@@ -119,7 +119,7 @@ RemoveObjects(DropStmt *stmt)
 	}
 
 	/* Here we really delete them. */
-	performMultipleDeletions(objects, stmt->behavior);
+	performMultipleDeletions(objects, stmt->behavior, 0);
 
 	free_object_addresses(objects);
 }

src/backend/commands/foreigncmds.c

@@ -1286,7 +1286,7 @@ RemoveUserMapping(DropUserMappingStmt *stmt)
 	object.objectId = umId;
 	object.objectSubId = 0;
 
-	performDeletion(&object, DROP_CASCADE);
+	performDeletion(&object, DROP_CASCADE, 0);
 }
 
 

src/backend/commands/opclasscmds.c

@@ -1519,7 +1519,7 @@ dropOperators(List *opfamilyname, Oid amoid, Oid opfamilyoid,
 		object.objectId = amopid;
 		object.objectSubId = 0;
 
-		performDeletion(&object, DROP_RESTRICT);
+		performDeletion(&object, DROP_RESTRICT, 0);
 	}
 }
 
@@ -1559,7 +1559,7 @@ dropProcedures(List *opfamilyname, Oid amoid, Oid opfamilyoid,
 		object.objectId = amprocid;
 		object.objectSubId = 0;
 
-		performDeletion(&object, DROP_RESTRICT);
+		performDeletion(&object, DROP_RESTRICT, 0);
 	}
 }
 

src/backend/commands/tablecmds.c

@@ -816,7 +816,7 @@ RemoveRelations(DropStmt *drop)
 		add_exact_object_address(&obj, objects);
 	}
 
-	performMultipleDeletions(objects, drop->behavior);
+	performMultipleDeletions(objects, drop->behavior, 0);
 
 	free_object_addresses(objects);
 }
@@ -4803,8 +4803,13 @@ ATExecColumnDefault(Relation rel, const char *colName,
 	 * Remove any old default for the column.  We use RESTRICT here for
 	 * safety, but at present we do not expect anything to depend on the
 	 * default.
+	 *
+	 * We treat removing the existing default as an internal operation when
+	 * it is preparatory to adding a new default, but as a user-initiated
+	 * operation when the user asked for a drop.
 	 */
-	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false);
+	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false,
+					  newDefault == NULL ? false : true);
 
 	if (newDefault)
 	{
@@ -5217,7 +5222,7 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
 	object.objectId = RelationGetRelid(rel);
 	object.objectSubId = attnum;
 
-	performDeletion(&object, behavior);
+	performDeletion(&object, behavior, 0);
 
 	/*
 	 * If we dropped the OID column, must adjust pg_class.relhasoids and tell
@@ -6731,7 +6736,7 @@ ATExecDropConstraint(Relation rel, const char *constrName,
 		conobj.objectId = HeapTupleGetOid(tuple);
 		conobj.objectSubId = 0;
 
-		performDeletion(&conobj, behavior);
+		performDeletion(&conobj, behavior, 0);
 
 		found = true;
 
@@ -7453,7 +7458,8 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 		 * We use RESTRICT here for safety, but at present we do not expect
 		 * anything to depend on the default.
 		 */
-		RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, true);
+		RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, true,
+						  true);
 
 		StoreAttrDefault(rel, attnum, defaultexpr);
 	}
@@ -7598,7 +7604,7 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
 		obj.classId = ConstraintRelationId;
 		obj.objectId = lfirst_oid(oid_item);
 		obj.objectSubId = 0;
-		performDeletion(&obj, DROP_RESTRICT);
+		performDeletion(&obj, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
 	}
 
 	foreach(oid_item, tab->changedIndexOids)
@@ -7606,7 +7612,7 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
 		obj.classId = RelationRelationId;
 		obj.objectId = lfirst_oid(oid_item);
 		obj.objectSubId = 0;
-		performDeletion(&obj, DROP_RESTRICT);
+		performDeletion(&obj, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
 	}
 
 	/*
@@ -9764,7 +9770,14 @@ PreCommit_on_commit_actions(void)
 					object.classId = RelationRelationId;
 					object.objectId = oc->relid;
 					object.objectSubId = 0;
-					performDeletion(&object, DROP_CASCADE);
+
+					/*
+					 * Since this is an automatic drop, rather than one
+					 * directly initiated by the user, we pass the
+					 * PERFORM_DELETION_INTERNAL flag.
+					 */
+					performDeletion(&object,
+									DROP_CASCADE, PERFORM_DELETION_INTERNAL);
 
 					/*
 					 * Note that table deletion will call

src/backend/commands/typecmds.c

@@ -2318,7 +2318,7 @@ AlterDomainDropConstraint(List *names, const char *constrName,
 			conobj.objectId = HeapTupleGetOid(contup);
 			conobj.objectSubId = 0;
 
-			performDeletion(&conobj, behavior);
+			performDeletion(&conobj, behavior, 0);
 			found = true;
 		}
 	}

src/backend/postmaster/autovacuum.c

@@ -2044,7 +2044,7 @@ do_autovacuum(void)
 					object.classId = RelationRelationId;
 					object.objectId = relid;
 					object.objectSubId = 0;
-					performDeletion(&object, DROP_CASCADE);
+					performDeletion(&object, DROP_CASCADE, PERFORM_DELETION_INTERNAL);
 				}
 				else
 				{

src/backend/storage/large_object/inv_api.c

@@ -307,7 +307,7 @@ inv_drop(Oid lobjId)
 	object.classId = LargeObjectRelationId;
 	object.objectId = lobjId;
 	object.objectSubId = 0;
-	performDeletion(&object, DROP_CASCADE);
+	performDeletion(&object, DROP_CASCADE, 0);
 
 	/*
 	 * Advance command counter so that tuple removal will be seen by later

src/include/catalog/dependency.h

@@ -152,11 +152,13 @@ typedef enum ObjectClass
 
 /* in dependency.c */
 
+#define PERFORM_DELETION_INTERNAL			0x0001
+
 extern void performDeletion(const ObjectAddress *object,
-				DropBehavior behavior);
+				DropBehavior behavior, int flags);
 
 extern void performMultipleDeletions(const ObjectAddresses *objects,
-						 DropBehavior behavior);
+						 DropBehavior behavior, int flags);
 
 extern void deleteWhatDependsOn(const ObjectAddress *object,
 					bool showNotices);

src/include/catalog/heap.h

@@ -107,7 +107,7 @@ extern void DeleteRelationTuple(Oid relid);
 extern void DeleteAttributeTuples(Oid relid);
 extern void RemoveAttributeById(Oid relid, AttrNumber attnum);
 extern void RemoveAttrDefault(Oid relid, AttrNumber attnum,
-				  DropBehavior behavior, bool complain);
+				  DropBehavior behavior, bool complain, bool internal);
 extern void RemoveAttrDefaultById(Oid attrdefId);
 extern void RemoveStatistics(Oid relid, AttrNumber attnum);