EF 4.3.1迁移异常 - AlterColumn defaultValueSql为不同的表创建相同的默认约束名称

Question

我有一个使用OOB数据库初始化程序创建的数据库,我使用的是Code First和EF 4.3.1.

我想利用Add-Migration cmdlet上的新"IgnoreChanges"标志,以便我可以更改一些列并添加默认SQL值.本质上,我的一些实体有一个名为DateLastUpdated的列,我想将DEFAULT设置为sql表达式GETDATE().

我使用"add-migration InitialMigration -ignorechanges"创建了InitialMigration,然后我将以下内容添加到Up()和Down():

public override void Up()
{
    AlterColumn("CustomerLocations", "DateLastUpdated", c => c.DateTime(defaultValueSql: "GETDATE()"));
    AlterColumn("UserReportTemplates", "DateLastUpdated", c => c.DateTime(defaultValueSql: "GETDATE()"));
    AlterColumn("Chains", "DateLastUpdated", c => c.DateTime(defaultValueSql: "GETDATE()"));
}

public override void Down()
{
    AlterColumn("CustomerLocations", "DateLastUpdated", c => c.DateTime());
    AlterColumn("UserReportTemplates", "DateLastUpdated", c => c.DateTime());
    AlterColumn("Chains", "DateLastUpdated", c => c.DateTime());
}

然后我尝试运行"Update-Database -verbose",但我发现它正在尝试在数据库上创建相同的命名默认约束,并且SQL抛出异常:

Applying explicit migrations: [201203221856095_InitialMigration].
Applying explicit migration: 201203221856095_InitialMigration.
ALTER TABLE [CustomerLocations] ADD CONSTRAINT DF_DateLastUpdated DEFAULT GETDATE() FOR [DateLastUpdated]
ALTER TABLE [CustomerLocations] ALTER COLUMN [DateLastUpdated] [datetime]
ALTER TABLE [UserReportTemplates] ADD CONSTRAINT DF_DateLastUpdated DEFAULT GETDATE() FOR [DateLastUpdated]
System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'DF_DateLastUpdated' in the database.
Could not create constraint. See previous errors.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at System.Data.Entity.Migrations.DbMigrator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable`1 migrationStatements)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable`1 migrationStatements)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, XDocument targetModel, IEnumerable`1 operations, Boolean downgrading)
   at System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore()
   at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()
There is already an object named 'DF_DateLastUpdated' in the database.
Could not create constraint. See previous errors.

看起来EF正在创建DEFAULT约束,方法是将"DF_"附加到列的名称,但不使用表的名称,以使其对表具有唯一性.这是一个已知的错误,还是我在这里做错了什么？

Answer 1

这似乎是一个已知的bug:msdn论坛

Andrew J Peters Microsoft(MSFT)回复:

感谢您报告此事.RTM将解决该问题.

一种可能的解决方法是最初使列可以为空,这将阻止迁移生成额外的DEFAULT约束.创建列后,可以将其更改为不可为空.

但它的定义并未在EF 4.3.1中修复.以下是来源的相关部分:

// Type: System.Data.Entity.Migrations.Sql.SqlServerMigrationSqlGenerator
// Assembly: EntityFramework, Version=4.3.1.0, 
// Culture=neutral, PublicKeyToken=b77a5c561934e089
namespace System.Data.Entity.Migrations.Sql
{
  public class SqlServerMigrationSqlGenerator : MigrationSqlGenerator
  {
     protected virtual void Generate(AlterColumnOperation alterColumnOperation)
     {
      //...
      writer.Write("ALTER TABLE ");
      writer.Write(this.Name(alterColumnOperation.Table));
      writer.Write(" ADD CONSTRAINT DF_");
      writer.Write(column.Name);
      writer.Write(" DEFAULT ");
      //...

因此EF不会尝试使约束名称唯一.

您应该尝试解决方法并将其报告为错误.

编辑:我刚刚意识到上面提到的Generate方法是virtual这样的,在最坏的情况下,你可以继承SqlServerMigrationSqlGenerator并修复SQL生成并将其设置为Configuration.cs中的sql生成器:

public Configuration()
{
    AutomaticMigrationsEnabled = true;
    SetSqlGenerator("System.Data.SqlClient", 
        new MyFixedSqlServerMigrationSqlGenerator());
}

编辑2:

我认为最好的办法是直到它恢复到原始SQL:

public override void Up()
{
    Sql(@"ALTER TABLE [CustomerLocations] ADD CONSTRAINT 
        DF_CustomerLocations_DateLastUpdated 
        DEFAULT GETDATE() FOR [DateLastUpdated]");
    Sql(@"ALTER TABLE [CustomerLocations] ALTER COLUMN 
        [DateLastUpdated] [datetime]");
    //...
}

Answer 2

好的,根据nemesv的回答(接受),这是我现在最终解决问题的方法,直到修正正式发布:

internal class MyFixedSqlServerMigrationSqlGenerator : SqlServerMigrationSqlGenerator
{
    protected override void Generate(AlterColumnOperation alterColumnOperation)
    {
        if (alterColumnOperation == null)
            throw new ApplicationException("alterColumnOperation != null");

        ColumnModel column = alterColumnOperation.Column;
        if ((column.DefaultValue != null) || !string.IsNullOrWhiteSpace(column.DefaultValueSql))
        {
            using (IndentedTextWriter writer = Writer())
            {
                writer.Write("ALTER TABLE ");
                writer.Write(this.Name(alterColumnOperation.Table));
                writer.Write(" ADD CONSTRAINT DF_");
                writer.Write(alterColumnOperation.Table + "_"); //   <== THIS IS THE LINE THAT FIXES THE PROBLEM
                writer.Write(column.Name);
                writer.Write(" DEFAULT ");
                writer.Write(column.DefaultValue != null ? base.Generate(column.DefaultValue) : column.DefaultValueSql);
                writer.Write(" FOR ");
                writer.Write(this.Quote(column.Name));
                this.Statement(writer);
            }
        }
        using (IndentedTextWriter writer2 = Writer())
        {
            writer2.Write("ALTER TABLE ");
            writer2.Write(this.Name(alterColumnOperation.Table));
            writer2.Write(" ALTER COLUMN ");
            writer2.Write(this.Quote(column.Name));
            writer2.Write(" ");
            writer2.Write(this.BuildColumnType(column));
            if (column.IsNullable.HasValue && !column.IsNullable.Value)
            {
                writer2.Write(" NOT NULL");
            }
            this.Statement(writer2);
        }
    }
}


internal sealed class Configuration : DbMigrationsConfiguration<MyDbContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = true;

        SetSqlGenerator("System.Data.SqlClient", new MyFixedSqlServerMigrationSqlGenerator());
    }
    ...
}