数据库应用所有以前的迁移上更新，而不只是新的 [英] Database applies ALL previous migrations on update and NOT just the new one

问题描述

我正在开发一个网站，目前，它有一个生产和测试数据库。
生产数据库在外部托管，而测试数据库托管在本地。

每当我对数据库进行更改时，我通过迁移应用更改。
添加新迁移之后，我在我的生产和测试数据库上运行 update-database 命令，使它们保持同步。

我将迁移应用到我的生产数据库，但是，当我想将迁移应用到我的测试数据库时，我看到它尝试应用所有以前的迁移（而不只是新的迁移）：

这是输出：

应用显式迁移：[201603230047093_Initial，
201603232305269_AddedBlobNameToImage，
201603242121190_RemovedSourceFromRealestateDbTable，
201603311617077_AddedSourceUrlId，
201604012033331_AddedIndexProfileAndFacebookNotifications，
201604012233271_RemovedTenantIndexProfile，
201604042359214_AddRealestateFilter]。应用显式迁移：
201603230047093_Initial。 System.Data.SqlClient.SqlException
（0x80131904）：
数据库中已经有一个名为Cities的对象。

显然，它失败，因为数据库的当前状态是第二次最新的迁移。但是，我不知道为什么它试图应用所有以前的迁移？

与生产数据库（一次已应用一个迁移）不同，测试数据库删除和创建，因此其迁移历史记录表只包含一行：

  201604012239054_InitialCreate 
  

（假设InitialCreate是所有以前迁移的自动生成的名称）。

总结：

为什么测试数据库试图应用所有先前的迁移，而不仅仅是新添加的？

编辑：
当运行COMMMAND时，我得到以下输出脚本：

  DECLARE @CurrentMigration [nvarchar]（max）
 
如果object_id（'[dbo]。[__ MigrationHistory]'）IS NOT NULL 
 SELECT @CurrentMigration = 
（SELECT TOP（1）
 [Project1]。[MigrationId] AS [MigrationId] 
 FROM（SELECT 
 [Extent1]。[MigrationId] AS [MigrationId] 
 FROM [dbo]。[__ MigrationHistory] ​​AS [Extent1] 
 WHERE [Extent1]。[ContextKey] = N'Boligside.Migrations.Configuration'
）AS [Project1] 
 ORDER BY [ Project1]。[MigrationId] DESC）
 
如果@CurrentMigration IS NULL 
 SET @CurrentMigration ='0'
 
如果@CurrentMigration< '201603230047093_Initial'
  

（进行每个先前迁移的if语句）

我的数据库中的当前迁移表看起来如下（注意，第一行是一个日志框架，所以它不相关）：

另请参阅 http://jameschambers.com/2014/02/changing-the-namespace-with-entity- framework-6-0-code-first-databases /

I'm developing a website which, as of current, both has a production and a test database. The production database is hosted externally while the test database is hosted locally.

Whenever I make changes to my database I apply the changes through a migration. After having added a new migration I run the update-database command on both my production and test database to keep them in sync.

I applied the migration just fine to my production database, however, when I wanna apply the migration to my test database I see that it attempts to apply ALL the previous migrations (and not just the new one):

Here is the output:

Applying explicit migrations: [201603230047093_Initial, 201603232305269_AddedBlobNameToImage, 201603242121190_RemovedSourceFromRealestateDbTable, 201603311617077_AddedSourceUrlId, 201604012033331_AddedIndexProfileAndFacebookNotifications, 201604012233271_RemovedTenantIndexProfile, 201604042359214_AddRealestateFilter]. Applying explicit migration: 201603230047093_Initial. System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'Cities' in the database.

Obviously it fails since the current state of the database is at the second latest migration. However I wonder why it attempts to apply ALL the previous migrations?

Unlike the production database (which has had all the migrations applied one at a time), the test database was deleted and created at the previous migration so its migration history table only contains one row:

201604012239054_InitialCreate 

(I assume InitialCreate is an auto generated name of all the previous migrations combined).

In summary:

Why is the test database trying to apply ALL the previous migrations instead of just the newly added?

EDIT: When running COMMMAND I get the follow output script:

DECLARE @CurrentMigration [nvarchar](max)

IF object_id('[dbo].[__MigrationHistory]') IS NOT NULL
    SELECT @CurrentMigration =
        (SELECT TOP (1) 
        [Project1].[MigrationId] AS [MigrationId]
        FROM ( SELECT 
        [Extent1].[MigrationId] AS [MigrationId]
        FROM [dbo].[__MigrationHistory] AS [Extent1]
        WHERE [Extent1].[ContextKey] = N'Boligside.Migrations.Configuration'
        )  AS [Project1]
        ORDER BY [Project1].[MigrationId] DESC)

IF @CurrentMigration IS NULL
    SET @CurrentMigration = '0'

IF @CurrentMigration < '201603230047093_Initial'

(it proceeds making if statements for each previous migration)

The current migrations table in my database looks the following (note that the first row is for a logging framework so it's not related):

解决方案

One issue that can cause migrations to rerun is if your context key changes which can happen during refactoring. There are a couple of ways to solve this:

1) Update the old records in __MigrationHistory with the new values:

UPDATE [dbo].[__MigrationHistory]
   SET [ContextKey] = ‘New_Namespace.Migrations.Configuration’
 WHERE [ContextKey] = ‘Old_Namespace.Migrations.Configuration’

2) You can hard code the old context key into the constructor of your migration Configuration class:

public Configuration()
{
    AutomaticMigrationsEnabled = false;
    this.ContextKey = "Old_Namespace.Migrations.Configuration";
}

Here is a good article on how migrations run under the hood: https://msdn.microsoft.com/en-US/data/dn481501?f=255&MSPPError=-2147217396

See also http://jameschambers.com/2014/02/changing-the-namespace-with-entity-framework-6-0-code-first-databases/

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