Azure 中 ExecuteSqlCommand 的事务

Question

我将 EF 6 与 Azure Sql 数据库一起使用。根据 Microsoft 的说法，不支持用户发起的交易（参考：https://msdn.microsoft.com/en-us/data/dn307226#transactions）

现在，对于 EF 6，ExecuteSqlCommand 默认包装在事务中：

Starting with EF6 Database.ExecuteSqlCommand() by default will wrap the command in a transaction if one was not already present. (ref: https://msdn.microsoft.com/en-us/data/dn456843.aspx)

鉴于我的情况，我是否应该始终抑制这样的 ExecuteSqlCommand 事务行为：

context.Database.ExecuteSqlCommand(TransactionalBehavior.DoNotEnsureTransaction, @"TRUNCATE TABLE Person;");

Answer 1

您所指的此声明仅适用于重试策略：

When you have configured an execution strategy that results in retries ...

您链接到的文章并非特定于 Azure。 Azure SQL 数据库支持事务。

Answer 2

是否要使用TransactionalBehavior.DoNotEnsureTransaction取决于您是否希望在命令范围内有事务。这仅在批处理中有多个 T-SQL 语句时才有意义（据我所知）。

换句话说，如果你的执行策略有重试并且想要在一个事务中执行多个语句，它们必须像下面这样全部在一个批次中。

为了使交易跨越多个批次，必须使用 db.Database.BeginTransaction 创建它。 the document you linked 解释的显式 BeginTransaction 不允许与重试结合使用。无论重试策略如何，都允许 TransactionalBehavior.EnsureTransaction 创建的事务（因为它完全由 EF 管理）。

// INSERT is rolled back due to error
context.Database.ExecuteSqlCommand(
    TransactionalBehavior.EnsureTransaction,
    @"INSERT INTO MyTable (i) VALUES (1)
    RAISERROR('This exception was intentionally thrown', 16, 1)");

// INSERT is committed
context.Database.ExecuteSqlCommand(
    TransactionalBehavior.DoNotEnsureTransaction,
    @"INSERT INTO MyTable (i) VALUES (1)
    RAISERROR('This exception was intentionally thrown', 16, 1)");

测试程序如下。

    private static void Main(string[] args)
    {
        //c:>sqlcmd -E
        //1> create database EFTransaction
        //2> go
        //1> use EFTransaction
        //2> go
        //Changed database context to 'EFTransaction'.
        //1> create table MyTable (i int primary key)
        //2> go
        const string connectionString = "Server=(local);Database=EFTransaction;Integrated Security=SSPI";

        using (DbContext context = new DbContext(connectionString))
        {
            context.Database.ExecuteSqlCommand(
                TransactionalBehavior.DoNotEnsureTransaction,
                @"IF EXISTS (SELECT * FROM sys.tables where name = 'MyTable')
                    DROP TABLE [dbo].[MyTable]
                CREATE TABLE MyTable (i INT PRIMARY KEY)");
        }

        Console.WriteLine("Insert one row."); 
        using (DbContext context = new DbContext(connectionString))
        {
            context.Database.ExecuteSqlCommand(
                TransactionalBehavior.EnsureTransaction,
                @"INSERT INTO MyTable (i) VALUES (0)");
            // Notice that there is no explicit COMMIT command required.
        }

        // Sanity check in a different connection that the row really was committed
        using (DbContext context = new DbContext(connectionString))
        {
            int rows = context.Database.SqlQuery<int>(
                "SELECT COUNT(*) FROM MyTable").Single();
            Console.WriteLine("Rows: {0}", rows); // Rows: 1
        }

        Console.WriteLine();
        Console.WriteLine("Insert one row and then throw an error, all within a transaction.");
        Console.WriteLine("The error should cause the insert to be rolled back, so there should be no new rows");
        using (DbContext context = new DbContext(connectionString))
        {
            try
            {
                context.Database.ExecuteSqlCommand(
                    TransactionalBehavior.EnsureTransaction,
                    @"INSERT INTO MyTable (i) VALUES (1)
                    RAISERROR('This exception was intentionally thrown', 16, 1)");
            }
            catch (SqlException e)
            {
                Console.WriteLine(e.Message);
            }

            int rows = context.Database.SqlQuery<int>(
                "SELECT COUNT(*) FROM MyTable").Single();
            Console.WriteLine("Rows: {0}", rows); // Rows: 1
        }

        Console.WriteLine();
        Console.WriteLine("Insert one row and then throw an error, all within a transaction.");
        Console.WriteLine("The error will not cause the insert to be rolled back, so there should be 1 new row");
        using (DbContext context = new DbContext(connectionString))
        {
            try
            {
                context.Database.ExecuteSqlCommand(
                    TransactionalBehavior.DoNotEnsureTransaction,
                    @"INSERT INTO MyTable (i) VALUES (1)
                    RAISERROR('This exception was intentionally thrown', 16, 1)");
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }

            int rows = context.Database.SqlQuery<int>(
                "SELECT COUNT(*) FROM MyTable").Single();
            Console.WriteLine("Rows: {0}", rows); // Rows: 2
        }
    }

Azure 中 ExecuteSqlCommand 的事务

Transaction for ExecuteSqlCommand in Azure

c#

entity-framework

azure

azure-sql-database