Count Rows in Doctrine QueryBuilder

I’m using Doctrine’s QueryBuilder to build a query, and I want to get the total count of results from the query.

$repository = $em->getRepository('FooBundle:Foo');

$qb = $repository->createQueryBuilder('n')
        ->where('n.bar = :bar')
        ->setParameter('bar', $bar);

$query = $qb->getQuery();

//this doesn't work
$totalrows = $query->getResult()->count();

I just want to run a count on this query to get the total rows, but not return the actual results. (After this count query, I’m going to further modify the query with maxResults for pagination.)