public function getNumBytes($user = null)
{
$query = $this->getConnection()->createQueryBuilder();
$query->select('SUM(i.size)')->from($this->tableNames['imageinfo'], 'i');
if ($user) {
$query->where('i.user = :user')->setParameter(':user', $user);
}
$stmt = $query->execute();
return (int) $stmt->fetchColumn();
}