通过 NHibernate 使用无状态会话急切地获取曾孙集合

发布于 2024-11-02 23:01:26 字数 1781 浏览 0 评论 0原文

我正在使用 NHibernate 无状态会话将批量数据加载到数据库中。加载数据时，后面的实体需要查找以前的实体，以便将它们添加到子集合中。此操作涉及需要孙对象的数据，而孙对象又需要可用的曾孙集合。

标准如下所示：

var result = InternalRepository.CreateCritera<Root>()
                .SetResultTransformer(Transformers.DistinctRootEntity)
                .Add(Restrictions.IdEq(id))
                .SetFetchMode("Child", FetchMode.Eager)
                .CreateAlias("Child", "a", JoinType.LeftOuterJoin)
                .SetFetchMode("a.Grandchild", FetchMode.Eager)
                .CreateAlias("Grandchild", "b", JoinType.LeftOuterJoin)
                .SetFetchMode("b.GreatGrandchildCollection", FetchMode.Eager)
                .UniqueResult<Root>();

当我执行此操作时，TwoPhaseLoad 在 InitializeEntity 期间抛出异常，因为会话的持久性上下文实体条目为空：

at NHibernate.Engine.TwoPhaseLoad.InitializeEntity(Object entity, Boolean readOnly, ISessionImplementor session, PreLoadEvent preLoadEvent, PostLoadEvent postLoadEvent) in TwoPhaseLoad.cs: line 64
at NHibernate.Loader.Loader.InitializeEntitiesAndCollections(IList hydratedObjects, Object resultSetId, ISessionImplementor session, Boolean readOnly) in Loader.cs: line 603
at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in Loader.cs: line 472
at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in Loader.cs: line 243
at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) in Loader.cs: line 1694 
...

加载程序正在查找的实体是子实体。为什么这里的持久化上下文条目映射是空的？显然正在获取对象（生成正确的 SQL 并返回正确的结果），并且“Child”实体已正确创建。为什么实体构建状态不正确？这是否与无状态会话在急切加载期间如何使用临时持久性上下文有关？

原文

I'm using an NHibernate Stateless Session to load bulk data into the database. As data is loaded, later entities need to lookup previous entities in order to add them to child collections. This operation involves needing data on a grandchild object, which in turn needs a great-grandchild collection to be available.

The criteria looks like this:

var result = InternalRepository.CreateCritera<Root>()
                .SetResultTransformer(Transformers.DistinctRootEntity)
                .Add(Restrictions.IdEq(id))
                .SetFetchMode("Child", FetchMode.Eager)
                .CreateAlias("Child", "a", JoinType.LeftOuterJoin)
                .SetFetchMode("a.Grandchild", FetchMode.Eager)
                .CreateAlias("Grandchild", "b", JoinType.LeftOuterJoin)
                .SetFetchMode("b.GreatGrandchildCollection", FetchMode.Eager)
                .UniqueResult<Root>();

When I execute this, TwoPhaseLoad throws an exception during InitializeEntity since the session's persistence context entity entries are empty:

at NHibernate.Engine.TwoPhaseLoad.InitializeEntity(Object entity, Boolean readOnly, ISessionImplementor session, PreLoadEvent preLoadEvent, PostLoadEvent postLoadEvent) in TwoPhaseLoad.cs: line 64
at NHibernate.Loader.Loader.InitializeEntitiesAndCollections(IList hydratedObjects, Object resultSetId, ISessionImplementor session, Boolean readOnly) in Loader.cs: line 603
at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in Loader.cs: line 472
at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in Loader.cs: line 243
at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) in Loader.cs: line 1694 
...

The entity the loader is looking up is the Child entity. Why is the persistence context entries map empty here? The object is apparently being fetched (the correct SQL is generated and returns correct results), and the "Child" entity is created correctly. Why is the entity construction state incorrect? Does it have to do with how the stateless session uses the temporary persistence context during eager loads?

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