/*
* IsSystemRelation
- * True iff the relation is either a system catalog or toast table.
- * By a system catalog, we mean one that created in the pg_catalog schema
- * during initdb. User-created relations in pg_catalog don't count as
- * system catalogs.
+ * True iff the relation is either a system catalog or a toast table.
+ * See IsCatalogRelation for the exact definition of a system catalog.
*
- * NB: TOAST relations are considered system relations by this test
- * for compatibility with the old IsSystemRelationName function.
- * This is appropriate in many places but not all. Where it's not,
- * also check IsToastRelation or use IsCatalogRelation().
+ * We treat toast tables of user relations as "system relations" for
+ * protection purposes, e.g. you can't change their schemas without
+ * special permissions. Therefore, most uses of this function are
+ * checking whether allow_system_table_mods restrictions apply.
+ * For other purposes, consider whether you shouldn't be using
+ * IsCatalogRelation instead.
+ *
+ * This function does not perform any catalog accesses.
+ * Some callers rely on that!
*/
bool
IsSystemRelation(Relation relation)
bool
IsSystemClass(Oid relid, Form_pg_class reltuple)
{
- return IsToastClass(reltuple) || IsCatalogClass(relid, reltuple);
+ /* IsCatalogRelationOid is a bit faster, so test that first */
+ return (IsCatalogRelationOid(relid) || IsToastClass(reltuple));
}
/*
* IsCatalogRelation
- * True iff the relation is a system catalog, or the toast table for
- * a system catalog. By a system catalog, we mean one that created
- * in the pg_catalog schema during initdb. As with IsSystemRelation(),
- * user-created relations in pg_catalog don't count as system catalogs.
+ * True iff the relation is a system catalog.
+ *
+ * By a system catalog, we mean one that is created during the bootstrap
+ * phase of initdb. That includes not just the catalogs per se, but
+ * also their indexes, and TOAST tables and indexes if any.
*
- * Note that IsSystemRelation() returns true for ALL toast relations,
- * but this function returns true only for toast relations of system
- * catalogs.
+ * This function does not perform any catalog accesses.
+ * Some callers rely on that!
*/
bool
IsCatalogRelation(Relation relation)
{
- return IsCatalogClass(RelationGetRelid(relation), relation->rd_rel);
+ return IsCatalogRelationOid(RelationGetRelid(relation));
}
/*
- * IsCatalogClass
- * True iff the relation is a system catalog relation.
+ * IsCatalogRelationOid
+ * True iff the relation identified by this OID is a system catalog.
+ *
+ * By a system catalog, we mean one that is created during the bootstrap
+ * phase of initdb. That includes not just the catalogs per se, but
+ * also their indexes, and TOAST tables and indexes if any.
*
- * Check IsCatalogRelation() for details.
+ * This function does not perform any catalog accesses.
+ * Some callers rely on that!
*/
bool
-IsCatalogClass(Oid relid, Form_pg_class reltuple)
+IsCatalogRelationOid(Oid relid)
{
- Oid relnamespace = reltuple->relnamespace;
-
/*
- * Never consider relations outside pg_catalog/pg_toast to be catalog
- * relations.
- */
- if (!IsSystemNamespace(relnamespace) && !IsToastNamespace(relnamespace))
- return false;
-
- /* ----
- * Check whether the oid was assigned during initdb, when creating the
- * initial template database. Minus the relations in information_schema
- * excluded above, these are integral part of the system.
- * We could instead check whether the relation is pinned in pg_depend, but
- * this is noticeably cheaper and doesn't require catalog access.
+ * We consider a relation to be a system catalog if it has an OID that was
+ * manually assigned or assigned by genbki.pl. This includes all the
+ * defined catalogs, their indexes, and their TOAST tables and indexes.
*
- * This test is safe since even an oid wraparound will preserve this
- * property (cf. GetNewObjectId()) and it has the advantage that it works
- * correctly even if a user decides to create a relation in the pg_catalog
- * namespace.
- * ----
+ * This rule excludes the relations in information_schema, which are not
+ * integral to the system and can be treated the same as user relations.
+ * (Since it's valid to drop and recreate information_schema, any rule
+ * that did not act this way would be wrong.)
+ *
+ * This test is reliable since an OID wraparound will skip this range of
+ * OIDs; see GetNewObjectId().
*/
- return relid < FirstNormalObjectId;
+ return (relid < (Oid) FirstBootstrapObjectId);
}
/*
* IsToastRelation
* True iff relation is a TOAST support relation (or index).
+ *
+ * Does not perform any catalog accesses.
*/
bool
IsToastRelation(Relation relation)
{
+ /*
+ * What we actually check is whether the relation belongs to a pg_toast
+ * namespace. This should be equivalent because of restrictions that are
+ * enforced elsewhere against creating user relations in, or moving
+ * relations into/out of, a pg_toast namespace. Notice also that this
+ * will not say "true" for toast tables belonging to other sessions' temp
+ * tables; we expect that other mechanisms will prevent access to those.
+ */
return IsToastNamespace(RelationGetNamespace(relation));
}
}
/*
- * IsSystemNamespace
+ * IsCatalogNamespace
* True iff namespace is pg_catalog.
*
+ * Does not perform any catalog accesses.
+ *
* NOTE: the reason this isn't a macro is to avoid having to include
* catalog/pg_namespace.h in a lot of places.
*/
bool
-IsSystemNamespace(Oid namespaceId)
+IsCatalogNamespace(Oid namespaceId)
{
return namespaceId == PG_CATALOG_NAMESPACE;
}
* IsToastNamespace
* True iff namespace is pg_toast or my temporary-toast-table namespace.
*
+ * Does not perform any catalog accesses.
+ *
* Note: this will return false for temporary-toast-table namespaces belonging
* to other backends. Those are treated the same as other backends' regular
* temp table namespaces, and access is prevented where appropriate.
+ * If you need to check for those, you may be able to use isAnyTempNamespace,
+ * but beware that that does involve a catalog access.
*/
bool
IsToastNamespace(Oid namespaceId)
projects / postgresql / commitdiff