NHibernate 3.“ThenFetch”的替代方案在查询中

发布于 2024-10-14 04:13:53 字数 436 浏览 4 评论 0原文

我将 NHibernate 3.0 与 LINQ 提供程序和 QueryOver 一起使用。有时我想急切地加载相关数据，这时可以使用 LINQ 和 QueryOver 中的“Fetch”方法来救援。现在我有一个特殊的场景，我想不直接在第二层加载一个属性，例如：

Foo f = ...;
f.A.B.C

使用 LINQ 没有问题，因为您可以使用“ThenFetch”方法“链接”获取，例如：

var result = Session.Query<Foo>().Fetch(a => a.A).ThenFetch(b => b.B).ThenFetch(c => c.C).ToList();

在 QueryOver 中没有这样的方法，那么如何才能达到相同的结果呢？

提前致谢。

原文

I'm using NHibernate 3.0 with both the LINQ provider and QueryOver. Sometimes I want to eager load related data, and there comes the method "Fetch" to the rescue, both in LINQ and QueryOver. Now I have a special scenario where I want to eager load a property not directly on the second level, like:

Foo f = ...;
f.A.B.C

with LINQ there's no problem, as you can "chain" fetches with the method "ThenFetch", like:

var result = Session.Query<Foo>().Fetch(a => a.A).ThenFetch(b => b.B).ThenFetch(c => c.C).ToList();

In QueryOver there's no such method, so how can I achieve the same result?

Thanks in advance.

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我很OK 2024-10-21 04:13:53

我实际上设法使用两种不同的方法来解决这个问题：

方法一：

Session.QueryOver<Foo>().Fetch(x => x.A).Fetch(x => x.A.B).Fetch(x => x.A.B.C)

方法二：

A a = null;
B b = null;
C c = null;

Session.QueryOver<Foo>()
    .JoinAlias(x => x.A, () => a)
    .JoinAlias(() => a.B, () => b)
    .JoinAlias(() => b.C, () => c)

两者都有效（尽管我不确定其中一个是否生成“内部”连接，另一个“外部”连接）。

I actually managed to solve this problem using two different approaches:

Approach one:

Session.QueryOver<Foo>().Fetch(x => x.A).Fetch(x => x.A.B).Fetch(x => x.A.B.C)

Approach two:

A a = null;
B b = null;
C c = null;

Session.QueryOver<Foo>()
    .JoinAlias(x => x.A, () => a)
    .JoinAlias(() => a.B, () => b)
    .JoinAlias(() => b.C, () => c)

Both work (altough I'm not exactly sure if one of them generated "inner" and the other one "outer" joins).

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灵芸 2024-10-21 04:13:53

出于好奇，我将在 NHibernate Jira：

query 
    .Fetch(p => p.B) 
    .Fetch(p => p.B.C) // if B is not a collection ... or 
    .Fetch(p => p.B[0].C) // if B is a collection ... or 
    .Fetch(p => p.B.First().C) // if B is an IEnumerable (using .First() extension method)

Just as a curiosity, I'll post the reply they gave me on the NHibernate Jira:

query 
    .Fetch(p => p.B) 
    .Fetch(p => p.B.C) // if B is not a collection ... or 
    .Fetch(p => p.B[0].C) // if B is a collection ... or 
    .Fetch(p => p.B.First().C) // if B is an IEnumerable (using .First() extension method)

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江心雾 2024-10-21 04:13:53

我认为你可以用 JoinQueryOver 做到这一点

IQueryOver<Relation> actual =
   CreateTestQueryOver<Relation>()
    .Inner.JoinQueryOver(r => r.Related1)
    .Left.JoinQueryOver(r => r.Related2)
    .Right.JoinQueryOver(r => r.Related3)
    .Full.JoinQueryOver(r => r.Related4)
    .JoinQueryOver(r => r.Collection1, () => collection1Alias)
    .Left.JoinQueryOver(r => r.Collection2, () => collection2Alias)
    .Right.JoinQueryOver(r => r.Collection3)
    .Full.JoinQueryOver(r => r.People, () => personAlias);

I think you can do that with JoinQueryOver

IQueryOver<Relation> actual =
   CreateTestQueryOver<Relation>()
    .Inner.JoinQueryOver(r => r.Related1)
    .Left.JoinQueryOver(r => r.Related2)
    .Right.JoinQueryOver(r => r.Related3)
    .Full.JoinQueryOver(r => r.Related4)
    .JoinQueryOver(r => r.Collection1, () => collection1Alias)
    .Left.JoinQueryOver(r => r.Collection2, () => collection2Alias)
    .Right.JoinQueryOver(r => r.Collection3)
    .Full.JoinQueryOver(r => r.People, () => personAlias);

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