Nhibernate Query和OrderBy导致同一个表上的多个连接

Question

模型中的两个核心实体是：

• 帐户
• 注册

以下是帐户和注册之间的fluentNH映射：

.Override<Account>(m =>
 {
   m.References(x =>
     x.Registration).Cascade.All().Not.Nullable().Unique(); 
     // unidirectional one-to-one association, unique will not allow multiple nulls
 }

我们有一个查询来查找前十名（accountid，registrationid） 匹配某个筛选条件（帐户中的表达式）并且是 按注册的两个字段排序

示例：

 public class AccountRegistrationId
{
  public Guid AccountId { get; set; }
  public Guid RegistrationId { get; set; }
}

THE QUERY：

查询：

(from r in _session.Query<Account>() select r)
.OrderBy(a => a.Registration.PatientVisit)
.OrderBy(a => a.Registration.AccountNumber)
.Where(a=>a.Registration.Mrn == "Mrn 1234")
.Select(a =>  new AccountRegistrationId{     AccountId = a.Id,
                                                                RegistrationId = a.Registration.Id
                                                          }
).ToArray();

生成的sql在帐户和帐户之间有4个外连接 注册

select   TOP ( 10 /* @p0 */ ) account0_.Id    as col_0_0_,
                     registrati3_.Id as col_1_0_
from     [Account] account0_
         left outer join [Registration] registrati1_
           on account0_.Registration_id = registrati1_.Id
         left outer join [Registration] registrati2_
           on account0_.Registration_id = registrati2_.Id
         left outer join [Registration] registrati3_
           on account0_.Registration_id = registrati3_.Id,
         [Registration] registrati4_

问题：多个左外连接注册表

• 投影的一个联接
• Where Criteria的一次加入
• OrderBy条件的两个连接（每个订单一个）

有没有在注册时摆脱这些多连接？