NHibernate fetch 创建正确的查询然后执行 N+1

Question

我有三个实体，配置为

Contact
  HasOne(e => e.User).PropertyRef(e => e.Contact).Cascade.All();

User
  HasMany(e => e.Requests);
  References(e => e.Contact);

Request
  References(e => e.User);

然后我这样查询：

  CurrentSession.Query<Request>()
                .Fetch(x => x.User)
                .ThenFetch(x => x.Contact)
                .ToList();

看起来 Fetch 正在运行，因为首先 select 我看到所有表都已连接（为简洁起见省略了其他字段）：

SELECT request0_.Id                 as Id128_0_,
   user1_.Id                       as Id131_1_,
   contact2_.Id                    as Id77_2_,
FROM   requests request0_
   left outer join users user1_
     on request0_.user_id = user1_.Id
   left outer join contacts contact2_
     on user1_.contact_id = contact2_.Id

然后由于某种原因关注 N+1 selects，我无法理解也不知道如何解决问题：

SELECT user0_.Id                as Id131_0_,
FROM   users user0_
WHERE  user0_.contact_id = 200 /* @p0 - contact_id */

Answer 1

目前它是 NHibernate 中的 bug。

NHibernate fetch 创建正确的查询然后执行 N+1

NHibernate fetch creates right query and then performs N+1

c#

nhibernate

fluent-nhibernate

fluent-nhibernate-mapping