Doctrine 1.2原始SQL分页

i'm using Symfony 1.4 with Doctrine 1.2. And i have this problem: I want to do a Pagination on my Native Query. The logic is like this:

1-

$statement = Doctrine_Manager::getInstance()->connection();
$query1 = $statement->execute(" SELECT * FROM table1 ");
$query1->fetchAll(PDO::FETCH_ASSOC);

2-

$pager = new sfDoctrinePager('MotherTable', 20);
--- The $query1 that comes as an Assoc array. 
$pager->setQuery( $query1 );
$pager->setPage( $request->getParameter('page', 1) );
$pager->init()

Any ideas? Thanks in advance