在 EF Core 中指定 Azure SQL 服务器版本而不中断本地开发

Question

Entity Framework Core 引入了 HasServiceTier 和 HasPerformanceLevel 方法来更改 Azure SQL 服务器的版本。您可以像这样在OnModelCreating 中使用它们：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.HasServiceTier("Basic");
    modelBuilder.HasPerformanceLevel("Basic");
}

如果你使用 Add-Migration Add-Migration 你会得到这样的迁移：

public partial class ChangedDatabaseServiceTierToBasic : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AlterDatabase()
            .Annotation("SqlServer:EditionOptions", "EDITION = 'Basic', SERVICE_OBJECTIVE = 'Basic'");
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AlterDatabase()
            .OldAnnotation("SqlServer:EditionOptions", "EDITION = 'Basic', SERVICE_OBJECTIVE = 'Basic'");
    }
}

这似乎工作正常，但是当我尝试将此迁移应用到本地非 Azure DB 以进行开发时，我收到以下错误：

Microsoft.EntityFrameworkCore.Migrations[20402]
      Applying migration '20200413102908_ChangedDatabaseServiceTierToBasic'.
Applying migration '20200413102908_ChangedDatabaseServiceTierToBasic'.
fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      BEGIN
      DECLARE @db_name NVARCHAR(MAX) = DB_NAME();
      EXEC(N'ALTER DATABASE ' + @db_name + ' MODIFY ( 
      EDITION = ''Basic'', SERVICE_OBJECTIVE = ''Basic'' );');
      END
Failed executing DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
BEGIN
DECLARE @db_name NVARCHAR(MAX) = DB_NAME();
EXEC(N'ALTER DATABASE ' + @db_name + ' MODIFY ( 
EDITION = ''Basic'', SERVICE_OBJECTIVE = ''Basic'' );');
END
Microsoft.Data.SqlClient.SqlException (0x80131904): Incorrect syntax near '.'.
   at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean isAsync, Int32 timeout, Boolean asyncWrite)
   at Microsoft.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String methodName)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteNonQuery(RelationalCommandParameterObject parameterObject)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
ClientConnectionId:d9f92b81-9916-48ee-9686-6d0f567ab86f
Error Number:102,State:1,Class:15
Incorrect syntax near '.'.

我假设这些命令对非 Azure DB 无效。那么问题来了：如何防止这些命令在非 Azure DB 上执行？

Answer 1

EF Core 团队现已意识到该问题并将其添加到他们的待办事项中： https://github.com/dotnet/efcore/issues/20682

同时官方推荐的解决方法如下：

migrationBuilder.Sql(@"IF SERVERPROPERTY('EngineEdition') = 5
EXEC(N'ALTER DATABASE [ThreeOne.SomeDbContext] MODIFY (EDITION = ''Basic'',  SERVICE_OBJECTIVE = ''Basic'' );');
");

我在不知道当前数据库名称的情况下对其进行了修改：

migrationBuilder.Sql
(
@"declare @dbname varchar(100)
set @dbname=quotename(db_name())
IF SERVERPROPERTY('EngineEdition') = 5
EXEC(N'ALTER DATABASE '+@dbname+' MODIFY (EDITION = ''Basic'', SERVICE_OBJECTIVE = ''Basic'' );');"
);

Answer 2

当然，非 Azure SQL 数据库不支持 EDITION 和 SERVICE_OBJECTIVE。

您只需为 Azure 数据库运行命令。对于其他类型的 SQL 服务器，您需要错过代码的执行。

我建议在运行代码之前检测SQL Server Edition。

为此，您可以添加扩展方法：

public static class DatabaseFacadeExtensions
{
    public static bool IsSqlAzure(this DatabaseFacade database)
    {
        var parameter = new SqlParameter("edition", SqlDbType.NVarChar)
        {
            Size = 128,
            Direction = ParameterDirection.Output
        };

        database.ExecuteSqlCommand("SELECT @edition = CAST(SERVERPROPERTY('Edition') AS NVARCHAR)", parameter);

        var edition = parameter.Value.ToString();

        return edition.Equals("SQL Azure", StringComparison.OrdinalIgnoreCase);
    }
}

在您的 OnModelCreating 方法中，您可以使用下一个代码：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    if (Database.IsSqlAzure())
    {
        modelBuilder.HasServiceTier("Basic");
        modelBuilder.HasPerformanceLevel("Basic");
    }
}

Answer 3

这感觉很不对，但确实有效：

public partial class ChangedDatabaseServiceTierToBasic : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        if (IsHostedInAzure())
        {
            migrationBuilder.AlterDatabase()
                .Annotation("SqlServer:EditionOptions", "EDITION = 'Basic', SERVICE_OBJECTIVE = 'Basic'");
        }
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        if (IsHostedInAzure())
        {
            migrationBuilder.AlterDatabase()
                .OldAnnotation("SqlServer:EditionOptions", "EDITION = 'Basic', SERVICE_OBJECTIVE = 'Basic'");
        }
    }

    private static bool IsHostedInAzure()
    {
        var env = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
        var config = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env}.json", optional: true, reloadOnChange: true)
            .Build();

        var isHostedInAzureConfig = config["DatabaseSettings:IsHostedInAzure"];
        var setEdition = bool.TryParse(isHostedInAzureConfig, out var isHostedInAzure) && isHostedInAzure;
        return setEdition;
    }
}