转换为按代码映射会导致主要的性能问题。

Question

我有一个NHibernate项目，它使用映射配置文件。我使用的是Server数据库。

我想通过代码转换到映射。我的方法是每次做一个类，确认所有的测试都通过了每一次转换。

将这两个映射混合在一起是非常直接的：

  public static ISessionFactory SessionFactory
  {
     get
     {
        if (_sessionFactory == null)
        {
           var configuration = new Configuration();

           configuration.Configure();
           configuration.AddAssembly(typeof(Entities.Player).Assembly);



           var mapper = new NHibernate.Mapping.ByCode.ModelMapper();
           // Here are the entities I've switched to mapping-by-code
           DATMedia.CMS.EntityLibrary.Mappings.ScheduleMediaItem.Map(mapper);
           DATMedia.CMS.EntityLibrary.Mappings.Schedule.Map(mapper);

           configuration.AddMapping(mapper.CompileMappingForAllExplicitlyAddedEntities());
           _sessionFactory = configuration.BuildSessionFactory();
        }
        return _sessionFactory;
     }
  }

然而，当我将Schedule映射更改为由代码映射时，我遇到了主要的性能问题。对Session.Flush的调用将花费12秒的时间，这超过了少量的测试数据。

我切换回XML映射，性能问题就消失了。

还有其他人经历过这个问题吗？

我将包括schedule的前后映射，以防出现明显的缺陷：

通过配置文件：

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
   <class name="DATMedia.CMS.EntityLibrary.Entities.Schedule, DATMedia.CMS.EntityLibrary" table="cms_Schedule">
      <id name="Id" column="Id" type="Int64">
         <generator class="identity" />
      </id>
      <property name="Date" column="Date" type="Timestamp" />
      <many-to-one name="SourceTemplate" column="SourceTemplate_Id" class="DATMedia.CMS.EntityLibrary.Entities.ScheduleTemplate, DATMedia.CMS.EntityLibrary" cascade="none" fetch="join" lazy="proxy"/>
     <!-- 
      Note that we are not using cascading deletes here.
      This will be handled by SQL Server through ON DELETE CASCADE foreign key constraints     
     -->
      <bag name="MediaItems" inverse="true" cascade="save-update" lazy="true" order-by="PlayIndex">
         <key column="Schedule_Id" />
         <one-to-many class="DATMedia.CMS.EntityLibrary.Entities.ScheduleMediaItem, DATMedia.CMS.EntityLibrary"/>
      </bag>
     <bag name="PlayerGroups" table="cms_ManyToMany_PlayerGroupSchedules_PlayerGroup_Schedule" lazy="true" cascade="save-update">
       <key column="Schedule_Id" />
       <many-to-many column="PlayerGroup_Id"
                     class="DATMedia.CMS.EntityLibrary.Entities.PlayerGroup, NHibernateManyToMany" />
     </bag>
   </class>
</hibernate-mapping>  

以及按代码绘制的地图：

    public static void Map(ModelMapper mapper)
    {
        mapper.Class<DATMedia.CMS.EntityLibrary.Entities.Schedule>(
            classMapper =>
            {
                classMapper.Table("cms_Schedule");
                classMapper.Id(x => x.Id, map =>
                    {
                        map.Column("Id");
                        map.Generator(Generators.Identity);
                    });
                classMapper.Property(
                        s => s.Date,
                        propertyMapper =>
                        {
                            propertyMapper.Column("Date");
                            propertyMapper.NotNullable(true);
                        }
                );
                classMapper.ManyToOne(
                                s => s.SourceTemplate,
                                manyToOneMapper =>
                                {
                                    manyToOneMapper.Column("SourceTemplate_Id");
                                    manyToOneMapper.Cascade(Cascade.None);
                                    manyToOneMapper.Fetch(FetchKind.Join);
                                    manyToOneMapper.Lazy(LazyRelation.Proxy);
                                }
                );
                classMapper.Bag(
                            s => s.MediaItems,
                            bagPropertyMapper =>
                            {
                                bagPropertyMapper.Key(keyMapper =>
                                                    {
                                                        keyMapper.Column("Schedule_Id");

                                                    }
                                );
                                bagPropertyMapper.Inverse(true);
                                bagPropertyMapper.Cascade(Cascade.Persist);
                                bagPropertyMapper.Lazy(CollectionLazy.Lazy);
                                bagPropertyMapper.OrderBy(smi => smi.PlayIndex);
                            }
                );
                classMapper.Bag(
                        s => s.PlayerGroups,
                        bagPropertyMapper =>
                        {
                            bagPropertyMapper.Key(keyMapper =>
                                {
                                    keyMapper.Column("Schedule_Id");
                                });

                            bagPropertyMapper.Table("cms_ManyToMany_PlayerGroupSchedules_PlayerGroup_Schedule");
                            bagPropertyMapper.Lazy(CollectionLazy.Extra);
                            bagPropertyMapper.Cascade(Cascade.Persist);
                        },
                        collectionElementRelation =>
                            {
                                collectionElementRelation.ManyToMany(manyToManyMapper =>
                                    {
                                        manyToManyMapper.Column("PlayerGroup_Id");
                                    }
                                );
                            }
                    );
            }

            );
    }

​

稍后编辑

​

我没有在事务中调用Flush，从而解决了这个问题。

我试图创建一些更简单的测试代码来复制这个问题，但是没有成功(我所有的测试代码都运行得非常快，不管我调用了多少次刷新)。这可能是因为我将一些实体的密钥生成从Identity转换为HiLo。

因此，在我的例子中，我的代码创建了一个特定的配置，这带来了一个问题，希望这不会再困扰我。

如果我猜到了，我会说导致问题的配置涉及到对长时间运行的事务的轻率使用和身份密钥生成相结合。

Answer 1

我在许多项目中使用了混合映射，并且没有遇到您所描述的任何问题。我不明白为什么冲水要花12秒。

我的混合映射技术与您的略有不同，而且我不能100%确定您配置的order是否重要，值得一试。请参阅http://puredotnetcoder.blogspot.co.uk/2011/07/mixed-mappings-with-hbm-and-mapping-by.html

我想您已经导出了所有的映射，并双重检查它们的在前后是否都是。请参阅http://puredotnetcoder.blogspot.co.uk/2011/07/view-xml-generated-when-mapping-by-code.html