protected function processAll($filepath, $preview = false)
    {
        $iterator = $this->getSource()->getIterator();
        $results = new BetterBulkLoader_Result();
        foreach ($iterator as $record) {
            if ($id = $this->processRecord($record, $this->columnMap, $results, $preview)) {
                $this->list->add($id);
            }
        }

        return $results;
    }