流利的NHibernate生成额外的列 [英] Fluent NHibernate generates extra columns

问题描述

我们在公司工作中使用流利的NHibernate作为数据对象模型。
几天前，我们遇到了一个问题，即Fluent NHibernate会生成一个额外的列，这个列在模型和映射中都不存在。这是情况：

我的模型：FirstClass.cs

  public class FirstClass 
 {
 public virtual int Id {get;私人设置} 
 public virtual SecondClass MyReference {get;组; } 
 public virtual DateTime DecisionDate {get;组; } 
 
 $ / code> 

我的贴图：



  public class FirstClassMap：ClassMap< FirstClass> 
 {
 public FirstClassMap（）
 {
 Id（x => x.Id）; 
 Map（x => x.DecisionDate）; 
 
参考文献（x => x.MyReference）; 
 
 
 
 
 $ b $ p $使用以下代码构建模式之后， （$）
 $ b $ pre $  Instance._sessionFactory = Fluently.Configure（）
 .Database（MySQLConfiguration.Standard 
 .ConnectionString（connectionString） 
 .ShowSql（））
 .ExposeConfiguration（c => 
 {
 c.Properties.Add（current_session_context_class，ConfigurationHelper.getSetting（SessionContext））; $ （）; 
。）
 .ExposeConfiguration（BuildSchema）
 .Mappings（m => m.FluentMappings.AddFromAssemblyOf< Community>））
 .BuildSessionFactory 
  

名为SecondClass_id的额外列是使用Id列的SecondClass表的索引和外键生成的。下面是生成的表格：

$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $' ，
`DecisionDate` datetime DEFAULT NULL，
`MyReference_id` int（11）DEFAULT NULL，
`SecondClass_id` int（11）DEFAULT NULL，
PRIMARY KEY ），
KEY`MyReference_id`（`MyReference_id`），
KEY`SecondClass_id`（`SecondClass_id`），
CONSTRAINT`FK4AFFB59B2540756F` FOREIGN KEY（`MyReference_id`）REFERENCES`SecondClass` ``Id`），
CONSTRAINT`FK4AFFB59B51EFB484` FOREIGN KEY（`SecondClass_id`）REFERENCES`SecondClass`（`Id`），
）ENGINE = InnoDB DEFAULT CHARSET = utf8;


我发现如果将MyReference重命名为SecondClass ），没有创建额外的列。但是我想用我指定的名字而不是类名来使用我的属性。为什么额外的列被创建？我如何解决这个问题？我不希望额外的外键列悬空。

解决方案

当您使用FNH并且您拥有实体之间的双向关系。



  public class FirstClass 
 {
 public virtual SecondClass MyReference {get;组; } 
} 
 
 public class SecondClass 
 {
 public virtual List< FirstClass> ListOfFirstClass {get;组; } 
} 
 
 public class FirstClassMap：ClassMap< FirstClass> 
 {
 public FirstClassMap（）
 {
 References（x => x.MyReference）; 
} 
} 
 
 public class SecondClassMap：ClassMap< SecondClass> 
 {
 Public SecondClassMap（）
 {
 HasMany（x => x.ListOfFirstClass）; 
 
 
 
 
 
 
为了解决这个问题，你必须覆盖使用的列名在任何一个ClassMap中，如下所示： 
 
 
  public class SecondClassMap：ClassMap< SecondClass> 
 {
 Public SecondClasssMap（）
 {
 HasMany（x => x.ListOfFirstClass）.KeyColumn（MyReference_id）; 
 
 
 code 
 
 
 
 
 
 
 
 
 $ b 
  public class FirstClassMap：ClassMap< FirstClass> 
 {
 public FirstClassMap（）
 {
 References（x => x.MyReference）.Column（SecondClass_id）; 
 
 
 
 
 $ p 
 $ b 
原因是FNH将每个映射视为一个单独的关系，因此不同的列，键和索引被创建。
 
We are using Fluent NHibernate for data object model in the company i work.
A couple of days ago, we encountered an issue that Fluent NHibernate generates an extra column which does exist neither in model nor in mapping. Here is the situation:

My Model: FirstClass.cs
public class FirstClass
{
    public virtual int Id { get; private set; }
    public virtual SecondClass MyReference { get; set; }
    public virtual DateTime DecisionDate { get; set; }
}
My Mapping:
public class FirstClassMap : ClassMap<FirstClass>
{
    public FirstClassMap()
    {
        Id(x => x.Id);
        Map(x => x.DecisionDate);

        References(x => x.MyReference);
    }
}
After building the schema with the following code,
Instance._sessionFactory = Fluently.Configure()
                .Database(MySQLConfiguration.Standard
                    .ConnectionString(connectionString)
                    .ShowSql())
                .ExposeConfiguration(c =>
                {
                    c.Properties.Add("current_session_context_class", ConfigurationHelper.getSetting("SessionContext"));
                })
                .ExposeConfiguration(BuildSchema)
                .Mappings( m => m.FluentMappings.AddFromAssemblyOf<Community>())
                .BuildSessionFactory();
An extra column named "SecondClass_id" is produced with index and foreign key to SecondClass table with Id column. Here is the table produced:
CREATE TABLE `FirstClass` (
  `Id` int(11) NOT NULL AUTO_INCREMENT,
  `DecisionDate` datetime DEFAULT NULL,
  `MyReference_id` int(11) DEFAULT NULL,
  `SecondClass_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`Id`),
  KEY `MyReference_id` (`MyReference_id`),
  KEY `SecondClass_id` (`SecondClass_id`),
  CONSTRAINT `FK4AFFB59B2540756F` FOREIGN KEY (`MyReference_id`) REFERENCES `SecondClass` (`Id`),
  CONSTRAINT `FK4AFFB59B51EFB484` FOREIGN KEY (`SecondClass_id`) REFERENCES `SecondClass` (`Id`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
I found that, if I rename "MyReference" to "SecondClass" (same name as the class type), there is no extra column created. But i want to use my property with the name i specified, not with the class name. Why that extra column is created? How do i fix that? I don't want extra foreign key columns hanging around.
解决方案
This often happens when you're using FNH and you have a two-way relationship between entities.
public class FirstClass
{
    public virtual SecondClass MyReference { get; set; }
}

public class SecondClass
{
    public virtual List<FirstClass> ListOfFirstClass { get; set; }
}

public class FirstClassMap : ClassMap<FirstClass>
{
    public FirstClassMap()
    {
        References(x => x.MyReference);
    }
}

public class SecondClassMap : ClassMap<SecondClass>
{
    public SecondClassMap()
    {
        HasMany(x => x.ListOfFirstClass);
    }
}
To fix this you have to override the column name used in either ClassMap, like so:
public class SecondClassMap : ClassMap<SecondClass>
{
    public SecondClasssMap()
    {
        HasMany(x => x.ListOfFirstClass).KeyColumn("MyReference_id");
    }
}
or:
public class FirstClassMap : ClassMap<FirstClass>
{
    public FirstClassMap()
    {
        References(x => x.MyReference).Column("SecondClass_id");
    }
}
The reason for this is that FNH treats each mapping as a separate relationship, hence different columns, keys, and indexes get created.

                        
这篇关于流利的NHibernate生成额外的列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！