生成的标识符对于约束名称来说太长了

Question

我刚刚开始使用Entity Framework(4.3.1),并使用MySQL EF提供程序(6.5.4)创建了具有TPT继承的代码优先模型.在尝试创建数据库结构时,我收到一个MySQLException "Identifier name 'LongClassNameOne_TypeConstraint_From_ClassName2s_To_LongClassNameOnes' is too long"(这是将派生类的表与父类的表相关联的关系.)

   at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
   at MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int32& insertedId)
   at MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId, Int32& affectedRows, Int32& insertedId)
   at MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId, Boolean force)
   at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()
   at MySql.Data.MySqlClient.MySqlScript.Execute()
   at MySql.Data.MySqlClient.MySqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection)
   at System.Data.Objects.ObjectContext.CreateDatabase()
   at System.Data.Entity.Internal.DatabaseOperations.Create(ObjectContext objectContext)
   at System.Data.Entity.Internal.DatabaseCreator.CreateDatabase(InternalContext internalContext, Func`3 createMigrator, ObjectContext objectContext)
   at System.Data.Entity.Internal.InternalContext.CreateDatabase(ObjectContext objectContext)
   at System.Data.Entity.Database.Create()
   at System.Data.Entity.DropCreateDatabaseAlways`1.InitializeDatabase(TContext context)
   at System.Data.Entity.Database.<>c__DisplayClass2`1.<SetInitializerInternal>b__0(DbContext c)
   at System.Data.Entity.Internal.InternalContext.<>c__DisplayClass8.<PerformDatabaseInitialization>b__6()
   at System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action)
   at System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization()
   at System.Data.Entity.Internal.LazyInternalContext.<InitializeDatabase>b__4(InternalContext c)
   at System.Data.Entity.Internal.RetryAction`1.PerformAction(TInput input)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action`1 action)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase()
   at System.Data.Entity.Internal.InternalContext.Initialize()
   at System.Data.Entity.Internal.InternalContext.ForceOSpaceLoadingForKnownEntityTypes()
   at System.Data.Entity.DbContext.System.Data.Entity.Infrastructure.IObjectContextAdapter.get_ObjectContext()
   ...

如何控制此名称以使其更短,或强制将其修剪为64个字符的名称限制,或沿着这些行的某些内容？

Answer 1

您需要使用较短的表名,因为无法配置约束的名称.请注意,您无需更改类名即可.您可以使用Table属性或在OnModelCreating中使用.ToTable()方法.

Answer 2

为了扩展我之前的评论......

如果您只需更改表名 - 那么请使用OnModelCreating中的映射 - as @Pawel suggested这可能是最简单的解决方案.

但是,如果您只想更改关系的名称,

...通过提供自定义SqlGenerator(即SqlServerMigrationSqlGenerator),Configuration()您可以微观管理在需要时生成的实际sql(在某些一般情况下可能是通用的自动化解决方案).例如

public class MySqlGenerator : SqlServerMigrationSqlGenerator
{
    protected override void Generate(AddForeignKeyOperation addForeignKeyOperation)
    {
        if (addForeignKeyOperation.Name == "LongClassNameOne_TypeConstraint_From_ClassName2s_To_LongClassNameOnes")
            addForeignKeyOperation.Name = "MyCustomFKName";
        // addForeignKeyOperation.Name = "Test" + addForeignKeyOperation.Name;
        base.Generate(addForeignKeyOperation);
    }
}

...或者沿着这些方向的东西(你需要匹配,找到正确的命名 - 或者Name Length在需要的地方进行比较和缩短.在你的配置中(由迁移生成的文件)......

public Configuration()
{
    AutomaticMigrationsEnabled = false;
    SetSqlGenerator("MySQL provider??", new MySqlGenerator());
    // SetSqlGenerator("System.Data.SqlClient", new MySqlGenerator());
}

(注意:我不知道MySQL提供商的名字是什么)

...这应该改变关系的FK - 并且只要可以快速测试它就可以正常工作,因为关系名称在C#模型中并没有真正使用(通常只是一个数据库名称).