转换为按代码映射会导致严重的性能问题

Question

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

我想切换到按代码映射。我的方法是一次只上一节课，确认每次转换都通过了所有测试。

混合这两个映射是非常直接的：

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映射转换为按代码映射时，我遇到了主要的性能问题。对Session.Flush的调用将花费12秒，而这只是少量的测试数据。

我切换回XML映射，性能问题就消失了。

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>  

按代码映射：

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");
}
);
}
);
}
);
}

---

后期编辑

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，但没有成功(无论我调用Flush多少次，我所有的测试代码都运行得很快)。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，在我的情况下，我的代码创建了一个特定的配置，这带来了一个问题，希望这不会再次困扰我

如果我猜到的话，我会说导致问题的配置涉及对长时间运行的事务的轻率使用与身份密钥生成的组合。

Answer 1

我在很多项目中使用过混合映射，并且没有遇到任何问题。我不明白为什么冲洗需要12秒。

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

我认为您已经导出了所有映射，并仔细检查了它们前后是否相同。看见http://puredotnetcoder.blogspot.co.uk/2011/07/view-xml-generated-when-mapping-by-code.html