protected function _fetchMaxChunks() {
        $count = 'COUNT(*)';
        $model = $this->getModel();
        $select = clone $this->getSelect();
        $select->reset(Zend_Db_Select::COLUMNS)
               ->reset(Zend_Db_Select::FROM)
               ->reset(Zend_Db_Select::ORDER)
               ->reset(Zend_Db_Select::GROUP)
        ;
        $select->from($model->getName(), array('c' => $count));

        if ($max = $this->_fetchMaxChunksFromFilters($select)) {
            return $max;
        } else {
            $result = $model->fetchRow($select);
            return $result->c;
        }
    }