private void Assert_exists() {
assert_exists = false;
if (!conn.Meta_tbl_exists(sys_tbl.Tbl_name())) sys_tbl.Create_tbl();
}
public int Autonum_next(String key) {
if (assert_exists) Assert_exists();
int rv = sys_tbl.Assert_int_or(key, 1);
sys_tbl.Update_int(key, rv + 1);
return rv;
}