Nested Set Tree Classes Should be able to get all roots

The nested set tree class does not seem to have a function to allow one to retrieve all entries in a table using trees. It only seems to allow access to sub-trees. In other words, can it get the entire tree, all roots/parents and all children, just as a general function (not based on any particular supplied item_id)?

Using $this->get_subtree_data(0, $order_asc, $include_item); as suggested, does not work, because 0 returns nothing if it is used as the item_id, and if you use an overwrite, i.e.: $this->column_item_id = 'parent_id' to make 0 refer to the parent_id in the SQL generated by get_set_of_nodes_data(), it still fails, because that function returns an array $rows[(int) $row[$this->column_item_id]] = $row; in which each $row has the same parent_id key, so you only end up with one parent + one child in the end.

To get the entire tree of data, should it have a basic way to get everything, similar to:

SELECT * FROM table ORDER_BY left_id

More specifically, a function something like this does what we (naderman, EXreaction and myself) were sort of intending:

public function get_tree_data($order_asc = true)

{

	$rows = array();

	$sql = 'SELECT ' . implode(', ', $this->item_basic_data) . '

		FROM ' . $this->table_name . ' ' .

		$this->get_sql_where('WHERE') . '

		ORDER BY ' . $this->column_left_id . ' ' . ($order_asc ? 'ASC' : 'DESC');

	$result = $this->db->sql_query($sql);

	while ($row = $this->db->sql_fetchrow($result))

	{

		$rows[(int) $row[$this->column_item_id]] = $row;

	}

	$this->db->sql_freeresult($result);

	return $rows;

}