public function offsetUnset($key) {
		$_key = $this->sql->real_escape_string($key);
		if (!$this->sql->query("DELETE FROM `{$this->table}` WHERE `app` = '{$this->app}' AND `key` = '$_key'")) {
			throw new AppMetadata_Exception(
				"Unable to delete app metadata (`$_key`). {$this->sql->error}",
				AppMetadata_Exception::DELETE_FAIL
			);
		}
		
		$result = parent::offsetUnset($key);

		$this->updateDerivedValues($key);
		
		return $result;
	}