Relation try_table_open(Oid relationId, LOCKMODE lockmode)
void table_close(Relation relation, LOCKMODE lockmode)
Relation table_open(Oid relationId, LOCKMODE lockmode)
Relation table_openrv(const RangeVar *relation, LOCKMODE lockmode)
Relation table_openrv_extended(const RangeVar *relation, LOCKMODE lockmode, bool missing_ok)