为什么NHibernate的LINQ提供程序为GroupBy（）生成无效的T-SQL？

Question

我正在尝试对每个Products生成的Manufacturer的数量进行简单查询，但NHibernate不会生成MS SQL Server发现的有效的T-SQL。 / p>

session.Query<Product>()
    .GroupBy(p => p.Manufacturer)
    .Select(grp => new {Mftr = grp.Key.Name, ProductCount = grp.Count()})
    .ToList();

这似乎很简单，但NHibernate生成的SQL语句不包含所有必需的列名，因此在针对SQL Server 2008或SQL Server CE数据库运行时失败。如果我将相同的代码指向内存中的SQLite数据库，它可以正常工作。

更多信息如下，我还创建了small console application that demonstrates my problem。 如何解决此问题？

---

生成的SQL

select manufactur1_.Id,
    cast(count(*) as INT), 
    manufactur1_.Id, 
    manufactur1_.Name 
from "Product" product0_ 
    left outer join "Manufacturer" manufactur1_ 
    on product0_.Manufacturer_id=manufactur1_.Id 
group by manufactur1_.Id   -- Where's manufactur1_.Name?

实体

public class Product {
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual Manufacturer Manufacturer { get; set; }
}
public class Manufacturer {
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
}

FNH Mappings

public class ProductMap : ClassMap<Product> {
    public ProductMap() {
        Id(x => x.Id).GeneratedBy.HiLo("1");
        Map(x => x.Name);
        References(x => x.Manufacturer).Cascade.SaveUpdate().Not.Nullable();
    }
}

public class ManufacturerMap : ClassMap<Manufacturer> {
    public ManufacturerMap() {
        Id(x => x.Id) .GeneratedBy.HiLo("1");
        Map(x => x.Name);
    }
}

Answer 1

这是一个QueryOver版本......

//alias variables
Manufacturer m = null;
ManufacturerProducts dto = null;

var result = Session.QueryOver<Product>
    .Left.JoinAlias(x => x.Manufacturer, () => m)
    .SelectList(list => list
        .SelectGroup(() => m.Id).WithAlias(() => dto.Id)
        .SelectGroup(() => m.Name).WithAlias(() => dto.Name)
        .SelectCount(x => x.Id).WithAlias(() => dto.ProductCount))
    .TransformUsing(Transformers.AliasToBean<ManufacturerProducts>())
    .List<ManufacturerProducts>();