[NHibernate]获取分组查询的记录总数

项目使用NHibernate2.1.0。今天遇到一个很闹心的问题，我们有一个带分组的分页查询

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var q = Session.CreateQuery(@"select t.PMM,t.RetailPrice, ...                                 from WarehouseDetail as t                                where ...                                group by t.PMM,t.RetailPrice")                 .SetFirstResult(start)                 .SetMaxResults(limit);

由于UI控件的需要，还得把符合上面那个查询条件的总的记录数查出来，但是下面这个语句不行

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long total = Session.CreateQuery(@"select count(*)                                      from WarehouseDetail as t                                     where ...                                     group by t.PMM,t.RetailPrice")                     .UniqueResult<long>();

因为使用了分组之后，上面那个HQL返回的是每个分组的记录数，而不是总的记录数，所以上面那个语句会报“query did not return a unique result: 3”的异常，意思是查询结果是3条数据。
按照以往写普通SQL语句的思路，我们会想把它改成下面这种子查询的形式

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long total = Session.CreateQuery(@"select count(*)                                      from (select t.PMM                                              from WarehouseDetail as t                                             where ...                                             group by t.PMM,t.RetailPrice)")                     .UniqueResult<long>();

但是很可惜，NHibernate还不支持这种from子查询。
另一种写法，是使用count distict

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long total = Session.CreateQuery(@"select count(distinct t.PMM || t.RetailPrice)                                      from WarehouseDetail as t                                     where ...")                     .UniqueResult<long>();

可是TNND NHibernate 居然不支持在count()里面进行字符串连接操作！我诅咒NHibernate项目组一辈子买方便面都只有调料包！！
最后没法子，搞了一个有点无厘头的语句

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long total = Session.CreateQuery(@"select sum(count(*)/count(*))                                      from WarehouseDetail as t                                     group by t.PMM,t.RetailPrice");                     .UniqueResult<long>();