使用NHibernate性能问题获取大块数据

I have a block of 50k data. I use NHibernate to retrieve all (retrieving all is necessary). But as having large dataset which is created by joining 5-7 tables NHibernate takes around one minute. The main cause of slow fetching might be joining of tables for which NHibernate creates queryfor each row from each table. I understand it is necessary as NHibernate needs to map each row to an object, but this overhead must be removed.I have a block of 50k data. I use NHibernate to