public function getMaxRank(ConnectionInterface $con = null)
    {
        if (null === $con) {
            $con = Propel::getServiceContainer()->getReadConnection(CustomerGroupTableMap::DATABASE_NAME);
        }
        // shift the objects with a position lower than the one of object
        $this->addSelectColumn('MAX(' . CustomerGroupTableMap::RANK_COL . ')');
        $stmt = $this->doSelect($con);

        return $stmt->fetchColumn();
    }