function _get_index(&$app, $parent, $ref_parent, $table, $id)
{
    $id_parent = $app->db->column($table, $ref_parent, $id);
    $c = new cursor_sql();
    $c->set_source($table);
    $c->query("{$ref_parent}={$id_parent}");
    $i = 1;
    while ($row = $c->get()) {
        if ($row['id'] == $id) {
            return array($i, $c->size());
        }
        $i++;
    }
}