Refine our definition of what constitutes a system relation.

Although user-defined relations can't be directly created in
pg_catalog, it's possible for them to end up there, because you can
create them in some other schema and then use ALTER TABLE .. SET SCHEMA
to move them there.  Previously, such relations couldn't afterwards
be manipulated, because IsSystemRelation()/IsSystemClass() rejected
all attempts to modify objects in the pg_catalog schema, regardless
of their origin.  With this patch, they now reject only those
objects in pg_catalog which were created at initdb-time, allowing
most operations on user-created tables in pg_catalog to proceed
normally.

This patch also adds new functions IsCatalogRelation() and
IsCatalogClass(), which is similar to IsSystemRelation() and
IsSystemClass() but with a slightly narrower definition: only TOAST
tables of system catalogs are included, rather than *all* TOAST tables.
This is currently used only for making decisions about when
invalidation messages need to be sent, but upcoming logical decoding
patches will find other uses for this information.

Andres Freund, with some modifications by me.

4 files changed, 8 insertions, 7 deletions

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index f6a5bfe8d15..afc6a786508 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -1354,7 +1354,7 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
 			 * ones the dependency changes would change.  It's too late to be
 			 * making any data changes to the target catalog.
 			 */
-			if (IsSystemClass(relform1))
+			if (IsSystemClass(r1, relform1))
 				elog(ERROR, "cannot swap toast files by links for system catalogs");
 
 			/* Delete old dependencies */
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 2155252e4ad..9b97e44867a 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1824,6 +1824,7 @@ ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
 	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
 	{
 		Form_pg_class classtuple = (Form_pg_class) GETSTRUCT(tuple);
+		Oid			relid = HeapTupleGetOid(tuple);
 
 		if (classtuple->relkind != RELKIND_RELATION &&
 			classtuple->relkind != RELKIND_MATVIEW)
@@ -1835,7 +1836,7 @@ ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
 			continue;
 
 		/* Check user/system classification, and optionally skip */
-		if (IsSystemClass(classtuple))
+		if (IsSystemClass(relid, classtuple))
 		{
 			if (!do_system)
 				continue;
@@ -1850,7 +1851,7 @@ ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
 			continue;			/* got it already */
 
 		old = MemoryContextSwitchTo(private_context);
-		relids = lappend_oid(relids, HeapTupleGetOid(tuple));
+		relids = lappend_oid(relids, relid);
 		MemoryContextSwitchTo(old);
 	}
 	heap_endscan(scan);
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 3483107e595..1aa1ad91277 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -910,7 +910,7 @@ RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 					   rel->relname);
 
-	if (!allowSystemTableMods && IsSystemClass(classform))
+	if (!allowSystemTableMods && IsSystemClass(relOid, classform))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied: \"%s\" is a system catalog",
@@ -2105,7 +2105,7 @@ renameatt_check(Oid myrelid, Form_pg_class classform, bool recursing)
 	if (!pg_class_ownercheck(myrelid, GetUserId()))
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 					   NameStr(classform->relname));
-	if (!allowSystemTableMods && IsSystemClass(classform))
+	if (!allowSystemTableMods && IsSystemClass(myrelid, classform))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied: \"%s\" is a system catalog",
@@ -10872,7 +10872,7 @@ RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid, Oid oldrelid,
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS, rv->relname);
 
 	/* No system table modifications unless explicitly allowed. */
-	if (!allowSystemTableMods && IsSystemClass(classform))
+	if (!allowSystemTableMods && IsSystemClass(relid, classform))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied: \"%s\" is a system catalog",
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index d86e9ad2c7d..0008fc633ba 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -1174,7 +1174,7 @@ RangeVarCallbackForRenameTrigger(const RangeVar *rv, Oid relid, Oid oldrelid,
 	/* you must own the table to rename one of its triggers */
 	if (!pg_class_ownercheck(relid, GetUserId()))
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS, rv->relname);
-	if (!allowSystemTableMods && IsSystemClass(form))
+	if (!allowSystemTableMods && IsSystemClass(relid, form))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied: \"%s\" is a system catalog",