NHibernate Join获取(Kind)

Question

给出了团队->运动员关系，并询问了所有运动员。我对fetch="Join"有什么误解？此映射是否应导致通过join加载团队？当迭代运动员时，它仍然懒惰地加载团队。

public class AthleteMap : ClassMapping<Athlete>
{
        public AthleteMap()
        {
            ManyToOne(a => a.Team, o =>
                                       {
                                           o.Fetch(FetchKind.Join);
                                           o.Lazy(LazyRelation.NoLazy);
                                       }
                );    
        }    
}

它产生了这个HBM：

<class name="Athlete" table="Athletes">
    <id name="Id" type="Int32" />
    <property name="FirstName" />
    <property name="LastName" />
    <many-to-one name="Team" fetch="join" lazy="false" />
    <property name="Created" />
</class>

迭代：

var session = factory.OpenSession();

 foreach (var athlete in session.Query<Athlete>())
     Console.WriteLine("{0} {1}", athlete.FirstName, athlete.Team.Name); 

Answer 1

NHibernate Linq查询不使用映射的fetch策略。您必须像这样在linq查询中获取()。

var session = factory.OpenSession();

foreach (var athlete in session.Query<Athlete>().Fetch(x => x.Team))
   Console.WriteLine("{0} {1}", athlete.FirstName, athlete.Team.Name); 

映射文档中定义的获取策略会影响：

通过Get()或Load()

• retrieval进行的子选择检索在关联为navigated

• ICriteria时隐式发生查询

• HQL查询如果使用子选择抓取

来源：performance-fetching