使用MySQL中的事务插入数据时读取记录

Similar questions have been asked multiple times but I have gone through them and couldn't find a solution.

I am trying to import a simple CSV file containing around 500 orders into my database table. And I am using transactions as shown below.

        $dbAdapter->beginTransaction();
        $file = new SplFileObject($fileName, 'r');
        while(!$file->eof()){               
            try{
                $order = $file->fgetcsv();
                if(!$this->orderExists($order)){ 
                     $this->saveOrder($order);
                }
            } catch (Exception $ex) {
                $dbAdapter->rollBack();
                throw new Om_Model_Exception($ex->getMessage());
            }
        }
        $dbAdapter->commit();

This works fine. But the same CSV file can have duplicate orders and I need to skip them. To do that before inserting the order I am checking the database table to see if the order exists but this always returns false because the transaction is still running.

So my question is, is there a way to check for inserted records before the transaction is committed? (May be MySQL stores data in to a temporary table and I can query that).

I can solve this by storing orders into an array and checking the array for duplicates but this seems like a waste of lot of memory. And might not work properly if the order file is large.

Thanks for your help.