protected function parse_order( $alias = 'q' ) {

		if ( ! is_array( $this->args['order'] ) && $this->args['order'] === 'rand' ) {
			return new Order( Order::RAND );
		} elseif ( ! is_array( $this->args['order'] ) ) {
			throw new \InvalidArgumentException( "Order must either be 'rand' or an array of columns to directions." );
		}

		$white_list = $this->table->get_columns();

		foreach ( $this->args['order'] as $column => $direction ) {

			$direction = strtoupper( $direction );

			if ( ! in_array( $direction, array( Order::ASC, Order::DESC ) ) ) {
				throw new \InvalidArgumentException( "Invalid order direction $direction for column $column." );
			}

			$column = $this->translate_order_by_to_column_name( $column );

			if ( ! isset( $white_list[ $column ] ) ) {
				throw new \InvalidArgumentException( "Invalid order column $column." );
			}

			$column = "{$alias}.$column";

			if ( ! isset( $order ) ) {
				$order = new Order( $column, $direction );
			} else {
				$order->then( $column, $direction );
			}
		}

		if ( isset( $order ) ) {
			return $order;
		} else {
			return new Order( "{$alias}.{$this->table->get_primary_key()}", Order::ASC );
		}
	}