nHibernate在子查询中计数行 [英] nHibernate count rows in subquery

问题描述

如何在nHibernate中做这样的事情：

How can I do something like this in nHibernate:

select count(*)
from (subquery)

这是SQL中一个相当简单的查询，但是解决方案在nHibernate中并不那么明显。一个明显的解决方案是沿着以下行：

It is a rather simple query in SQL, but the solution is not so obvious in nHibernate. An obvious solution would be something along the line of:

    var rowcount = Session.QueryOver<Entity>()
       .Select(Projections.Alias(Projections.Count(Projections.SubQuery(detachedQuery)), "count"))
        .FutureValue<int>();

<

However, this results in an ArgumentOutOfRangeException:

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

这 SO答案不适用于我，因为我有一个更复杂的分组。
我的问题源自先前的问题，其中我尝试使用<$

This SO answer doesn't work for me, as I have a more complex grouping. My question originates from an earlier question where I tried to use ToRowCountQuery, but that function strips groupings form the query.

推荐答案

我发现一个老帖子由Ayende给我一个解决方案（计算分页数据）。

I found an old post by Ayende which gave me a solution (Counting paged data).

我创建了自己的方言，如该帖中所述，并添加了 rowcount 函数到我的分页查询。和presto，我得到我的行计数在单个查询到数据库。

I created my own dialect as described in that post and added the rowcount function to my paged query. And presto, I got my rowcount in a single query to the database.

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