带有tofuture的懒惰的儿童收集

Question

我目前正在使用nhibernate 3.2击中SQLServer数据库，我正在尝试使用多Queary's and Futures来加载子女收藏。

无论如何，我都可以使用linq进行NHIBERNATE来工作，但是当查看SQL被发送到数据库时，看起来好像它正在加载所有父对象，而除了子Collection for for Child collection fet fitch（如它急切地加载）。我很好奇是否可以更改此行为以仅拉出所需的子对象列。

这是一个说明此问题的代码的示例。

  public class Parent : Entity
   {
      public virtual string Name { get; set; }
      public virtual IList<Child> Children { get; set; }
   }

public class Child : Entity
   {
      public virtual int Age { get; set; }
      public virtual string Name { get; set; }
      public virtual Parent Parent { get; set; }
   }

public class ChildClassMap : ClassMap<Child>
   {
      public ChildClassMap()
      {
         Id(x => x.Id,"Id");
         Map(x => x.Age);
         Map(x => x.Name);
         this.References(x => x.Parent).Column("ParentId").ForeignKey("Id");
      }
   }

 public class ParentClassMap : ClassMap<Parent>
   {
      public ParentClassMap()
      {
         Id(x => x.Id, "Id");
         Map(x => x.Name);
         this.HasMany(x => x.Children).KeyColumn("ParentId");
      }
   }

  public class FamilyRepository : NHibernateRepository<Parent>
   {
      public Parent GetParent(int id)
      {
         using (var session = this.Session.OpenSession())
         {
            var parent = session.Query<Parent>()
               .Where(p => p.Id == id);
            parent.FetchMany(x => x.Children)
               .ToFuture();
            return parent.ToFuture().SingleOrDefault();
         }
      }
   }

测试用例

   [TestClass]
   public class FamilyTests
   {
      [TestMethod]
      public void Should_Get_Parent_And_Children()
      {
         // arrange
         var repo = new FamilyRepository();
         // act
         var parent = repo.GetParent(1);
         // assert
         Assert.AreNotEqual(null, parent);
         Assert.AreEqual("TheOldOne", parent.Name);
         Assert.AreEqual(3, parent.Children.Count);
         Assert.AreEqual(4, parent.Children[1].Age);
         Assert.AreEqual("TheMiddleOne", parent.Children[1].Name);
      }
   }

sql：

CREATE TABLE [dbo].[Parent](
   [Id] [int] IDENTITY(1,1) NOT NULL,
   [Name] [varchar](50) NOT NULL,
CONSTRAINT [PK_Parent] PRIMARY KEY CLUSTERED 
(
   [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
CREATE TABLE [dbo].[Child](
   [Id] [int] IDENTITY(1,1) NOT NULL,
   [ParentId] [int] NOT NULL,
   [Age] [int] NOT NULL,
   [Name] [varchar](50) NOT NULL,
CONSTRAINT [PK_Child] PRIMARY KEY CLUSTERED 
(
   [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[Child]  WITH CHECK ADD  CONSTRAINT [FK_Child_Parent] FOREIGN KEY([ParentId])
REFERENCES [dbo].[Parent] ([Id])
GO
ALTER TABLE [dbo].[Child] CHECK CONSTRAINT [FK_Child_Parent]
GO

Set Identity_Insert [dbo].[Parent] on 
insert into [dbo].[Parent]
(Id, Name)
values (1, 'TheOldOne');
insert into [dbo].[Parent]
(Id, Name)
values (2, 'TheOtherOne');
Set Identity_Insert [dbo].[Parent] off
GO
Set Identity_Insert [dbo].[Child] on
insert into [dbo].[Child]
(Id, ParentId, Age, Name)
values(1,1,3,'TheYoungOne')

insert into [dbo].[Child]
(Id, ParentId, Age, Name)
values(2,1,4,'TheMiddleOne')

insert into [dbo].[Child]
(Id, ParentId, Age, Name)
values(3,1,7,'TheFirstOne')
Set Identity_Insert [dbo].[Child] off

SQL Profiler的输出是：

exec sp_executesql N'
    select parent0_.Id as Id3_0_, children1_.Id as Id2_1_, parent0_.Name as Name3_0_, children1_.Age as Age2_1_, children1_.Name as Name2_1_, children1_.ParentId as ParentId2_1_, children1_.ParentId as ParentId0__, children1_.Id as Id0__ 
    from [Parent] parent0_ left outer join [Child] children1_ on parent0_.Id=children1_.ParentId where parent0_.Id=@p0;
    select parent0_.Id as Id3_, parent0_.Name as Name3_ from [Parent] parent0_ where parent0_.Id=@p1;
',N'@p0 bigint,@p1 bigint',@p0=1,@p1=1

有人有任何建议吗？

感谢您的时间

Answer 1

只需将代码缩短到

public Parent GetParentWithChildrenInitialised(int id)
{
    using (var session = SessionFactory.OpenSession())
    {
        return session.Query<Parent>()
           .Where(p => p.Id == id)
           .FetchMany(x => x.Children)
           .SingleOrDefault();
    }
}

我的个人会摆脱存储库，因为它添加了不必要的抽象，并且使调整性能更加困难，Isession已经像呼吸道一样。

一个更好的选择是使用session.Get(parentId);，因为如果需要孩子，则使用LVL1/会话缓存或上面的查询。

还使用SessionFactory创建会话，因为它是螺纹安全，sessions却不是。