我开始在我的生产代码中使用SQL Server的tSQLt单元测试。目前,我使用Erland Sommarskog的SQL Server错误处理模式。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.SommarskogRollback') IS NOT NULL
DROP PROCEDURE dbo.SommarskogRollback;
GO
CREATE PROCEDURE dbo.SommarskogRollback
AS
BEGIN; /*Stored Procedure*/
SET XACT_ABORT, NOCOUNT ON;
BEGIN TRY;
BEGIN TRANSACTION;
RAISERROR('This is just a test. Had this been an actual error, we would have given you some cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH;
IF @@TRANCOUNT > 0
ROLLBACK TRANSACTION;
THROW;
END CATCH;
END; /*Stored Procedure*/
GO
Erland Sommarskog建议我们始终设置XACT_ABORTON,因为只有这样SQL服务器才能以(大部分)一致的方式处理错误。
但是,这在使用tSQLt时产生了一个问题。tSQLt执行显式事务内部的所有测试。当测试完成时,整个事务回滚。这使得测试工件的清理完全没有痛苦。但是,当XACT _中止打开时,TRY块中抛出的任何错误都会立即导致事务失败。事务必须完全回滚。它不能提交,也不能回滚到保存点。事实上,在事务回滚之前,任何东西都不能写入该会话中的事务日志。然而,tSQLt不能正确地跟踪测试结果,除非测试结束时事务是打开的。tSQLt停止执行,并为注定失败的事务抛出回滚错误。失败的测试显示错误状态(而不是成功或失败),并且后续测试不会运行。
tSQL的创建者Sebastian Meine推荐了一种不同的错误处理模式。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.MeineRollback') IS NOT NULL
DROP PROCEDURE dbo.MeineRollback;
GO
CREATE PROCEDURE dbo.MeineRollback
AS
BEGIN /*Stored Procedure*/
SET NOCOUNT ON;
/* We declare the error variables here, populate them inside the CATCH
* block and then do our error handling after exiting the CATCH block
*/
DECLARE @ErrorNumber INT
,@MessageTemplate NVARCHAR(4000)
,@ErrorMessage NVARCHAR(4000)
,@ErrorProcedure NVARCHAR(126)
,@ErrorLine INT
,@ErrorSeverity INT
,@ErrorState INT
,@RaisErrorState INT
,@ErrorLineFeed NCHAR(1) = CHAR(10)
,@ErrorStatus INT = 0
,@SavepointName VARCHAR(32) = REPLACE( (CAST(NEWID() AS VARCHAR(36))), '-', '');
/*Savepoint names are 32 characters and must be unique. UNIQUEIDs are 36, four of which are dashes.*/
BEGIN TRANSACTION; /*If a transaction is already in progress, this just increments the transaction count*/
SAVE TRANSACTION @SavepointName;
BEGIN TRY;
RAISERROR('This is a test. Had this been an actual error, Sebastian would have given you a meaningful error message.', 16, 1);
END TRY
BEGIN CATCH;
/* Build a message string with placeholders for the original error information
* Note: "%d" & "%s" are placeholders (substitution parameters) which capture
* the values from the argument list of the original error message.
*/
SET @MessageTemplate = N': Error %d, Severity %d, State %d, ' + @ErrorLineFeed
+ N'Procedure %s, Line %d, ' + @ErrorLineFeed
+ N', Message: %s';
SELECT @ErrorStatus = 1
,@ErrorMessage = ERROR_MESSAGE()
,@ErrorNumber = ERROR_NUMBER()
,@ErrorProcedure = ISNULL(ERROR_PROCEDURE(), '-')
,@ErrorLine = ERROR_LINE()
,@ErrorSeverity = ERROR_SEVERITY()
,@ErrorState = ERROR_STATE()
,@RaisErrorState = CASE ERROR_STATE()
WHEN 0 /*RAISERROR Can't generate errors with State = 0*/
THEN 1
ELSE ERROR_STATE()
END;
END CATCH;
/*Rollback to savepoint if error occurred. This does not affect the transaction count.*/
IF @ErrorStatus <> 0
ROLLBACK TRANSACTION @SavepointName;
/*If this procedure executed inside a transaction, then the commit just subtracts one from the transaction count.*/
COMMIT TRANSACTION;
IF @ErrorStatus = 0
RETURN 0;
ELSE
BEGIN; /*Re-throw error*/
/*Rethrow the error. The msg_str parameter will contain the original error information*/
RAISERROR( @MessageTemplate /*msg_str parameter as message format template*/
,@ErrorSeverity /*severity parameter*/
,@RaisErrorState /*state parameter*/
,@ErrorNumber /*argument: original error number*/
,@ErrorSeverity /*argument: original error severity*/
,@ErrorState /*argument: original error state*/
,@ErrorProcedure /*argument: original error procedure name*/
,@ErrorLine /*argument: original error line number*/
,@ErrorMessage /*argument: original error message*/
);
RETURN -1;
END; /*Re-throw error*/
END /*Stored Procedure*/
GO
他声明错误变量,开始事务,设置保存点,然后在 TRY 块内执行过程代码。如果 TRY 块引发错误 ,则执行将传递到 CATCH 块,后者填充错误变量。然后执行从 TRY 捕获块中传递出来。出错时,事务将回滚到过程开始时设置的存储点。然后事务提交。由于 SQL Server 处理嵌套事务的方式,当在另一个事务中执行时,此 COMMIT 只是从事务计数器中减去一个。(嵌套事务在 SQL 服务器中实际上并不存在。
塞巴斯蒂安创造了一个非常整洁的图案。执行链中的每个过程都会清理自己的事务。不幸的是,这种模式有一个大问题:注定的交易。注定失败的事务会打破这种模式,因为它们无法回滚到保存点或提交。它们只能完全回滚。当然,这意味着在使用TRY-CATCH块时不能将XACT_ABORT设置为ON(并且应该始终使用TRY-CATCH块)。即使关闭了XACT_ ABORT,许多错误(如编译错误)仍会导致事务失败。此外,保存点不适用于分布式事务。
我如何解决这个问题?我需要一个错误处理模式,它可以在tSQL测试框架内工作,并在生产中提供一致、正确的错误处理。我可以在运行时检查环境并相应地调整行为。(请参阅下面的示例。)然而,我不喜欢这样。对我来说,这感觉就像是一种黑客攻击。它要求开发环境配置一致。更糟糕的是,我不测试我的实际生产代码。有人有出色的解决方案吗?
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.ModifiedRollback') IS NOT NULL
DROP PROCEDURE dbo.ModifiedRollback;
GO
CREATE PROCEDURE dbo.ModifiedRollback
AS
BEGIN; /*Stored Procedure*/
SET NOCOUNT ON;
IF RIGHT(@@SERVERNAME, 9) = '\LOCALDEV'
SET XACT_ABORT OFF;
ELSE
SET XACT_ABORT ON;
BEGIN TRY;
BEGIN TRANSACTION;
RAISERROR('This is just a test. Had this been an actual error, we would have given you some cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH;
IF @@TRANCOUNT > 0 AND RIGHT(@@SERVERNAME,9) <> '\LOCALDEV'
ROLLBACK TRANSACTION;
THROW;
END CATCH;
END; /*Stored Procedure*/
GO
编辑:经过进一步的测试,我发现我修改后的回滚也不起作用。当过程引发错误时,它将退出而不回滚或提交。tSQLt 会引发错误,因为过程退出时@@TRANCOUNT与过程启动时的计数不匹配。经过一些尝试和错误,我找到了一个在我的测试中有效的解决方法。它结合了两种错误处理方法 - 使错误处理更加复杂,并且某些代码路径无法测试。我很想找到一个更好的解决方案。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.TestedRollback') IS NOT NULL
DROP PROCEDURE dbo.TestedRollback;
GO
CREATE PROCEDURE dbo.TestedRollback
AS
BEGIN /*Stored Procedure*/
SET NOCOUNT ON;
/* Due to the way tSQLt uses transactions and the way SQL Server handles errors, we declare our error-handling
* variables here, populate them inside the CATCH block and then do our error-handling after exiting
*/
DECLARE @ErrorStatus BIT
,@ErrorNumber INT
,@MessageTemplate NVARCHAR(4000)
,@ErrorMessage NVARCHAR(4000)
,@ErrorProcedure NVARCHAR(126)
,@ErrorLine INT
,@ErrorSeverity INT
,@ErrorState INT
,@RaisErrorState INT
,@ErrorLineFeed NCHAR(1) = CHAR(10)
,@FALSE BIT = CAST(0 AS BIT)
,@TRUE BIT = CAST(1 AS BIT)
,@tSQLtEnvironment BIT
,@SavepointName VARCHAR(32) = REPLACE( (CAST(NEWID() AS VARCHAR(36))), '-', '');
/*Savepoint names are 32 characters long and must be unique. UNIQUEIDs are 36, four of which are dashes*/
/* The tSQLt Unit Testing Framework we use in our local development environments must maintain open transactions during testing. So,
* we don't roll back transactions during testing. Also, doomed transactions can't stay open, so we SET XACT_ABORT OFF while testing.
*/
IF RIGHT(@@SERVERNAME, 9) = '\LOCALDEV'
SET @tSQLtEnvironment = @TRUE
ELSE
SET @tSQLtEnvironment = @FALSE;
IF @tSQLtEnvironment = @TRUE
SET XACT_ABORT OFF;
ELSE
SET XACT_ABORT ON;
BEGIN TRY;
SET ROWCOUNT 0; /*The ROWCOUNT setting can be updated outside the procedure and changes its behavior. This sets it to the default.*/
SET @ErrorStatus = @FALSE;
BEGIN TRANSACTION;
/*We need a save point to roll back to in the tSQLt Environment.*/
IF @tSQLtEnvironment = @TRUE
SAVE TRANSACTION @SavepointName;
RAISERROR('Cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
RETURN 0;
END TRY
BEGIN CATCH;
SET @ErrorStatus = @TRUE;
/* Build a message string with placeholders for the original error information
* Note: "%d" & "%s" are placeholders (substitution parameters) which capture
* the values from the argument list of the original error message.
*/
SET @MessageTemplate = N': Error %d, Severity %d, State %d, ' + @ErrorLineFeed
+ N'Procedure %s, Line %d, ' + @ErrorLineFeed
+ N', Message: %s';
SELECT @ErrorMessage = ERROR_MESSAGE()
,@ErrorNumber = ERROR_NUMBER()
,@ErrorProcedure = ISNULL(ERROR_PROCEDURE(), '-')
,@ErrorLine = ERROR_LINE()
,@ErrorSeverity = ERROR_SEVERITY()
,@ErrorState = ERROR_STATE()
,@RaisErrorState = CASE ERROR_STATE()
WHEN 0 /*RAISERROR Can't generate errors with State = 0*/
THEN 1
ELSE ERROR_STATE()
END;
END CATCH;
/* Due to the way the tSQLt test framework uses transactions, we use two different error-handling schemes:
* one for unit-testing and the other for our main Test/Staging/Production environments. In those environments
* we roll back transactions in the CATCH block in the event of an error. In unit-testing, on the other hand,
* we begin a transaction and set a save point. If an error occurs we roll back to the save point and then
* commit the transaction. Since tSQLt executes all test in a single explicit transaction, starting a
* transaction at the beginning of this stored procedure just adds one to @@TRANCOUNT. Committing the
* transaction subtracts one from @@TRANCOUNT. Rolling back to a save point does not affect @@TRANCOUNT.
*/
IF @ErrorStatus = @TRUE
BEGIN; /*Error Handling*/
IF @tSQLtEnvironment = @TRUE
BEGIN; /*tSQLt Error Handling*/
ROLLBACK TRANSACTION @SavepointName; /*Rolls back to save point but does not affect @@TRANCOUNT*/
COMMIT TRANSACTION; /*Subtracts one from @@TRANCOUNT*/
END; /*tSQLt Error Handling*/
ELSE IF @@TRANCOUNT > 0
ROLLBACK TRANSACTION;
/*Rethrow the error. The msg_str parameter will contain the original error information*/
RAISERROR( @MessageTemplate /*msg_str parameter as message format template*/
,@ErrorSeverity /*severity parameter*/
,@RaisErrorState /*state parameter*/
,@ErrorNumber /*argument: original error number*/
,@ErrorSeverity /*argument: original error severity*/
,@ErrorState /*argument: original error state*/
,@ErrorProcedure /*argument: original error procedure name*/
,@ErrorLine /*argument: original error line number*/
,@ErrorMessage /*argument: original error message*/
);
END; /*Error Handling*/
END /*Stored Procedure*/
GO
我正在测试一个补丁来修改框架过程tSQLt。Private_RunTest。基本上,在主CATCH块中,它试图做一个命名的回滚(对我来说是1448行),我替换了
ROLLBACK TRAN @TranName;
跟
IF XACT_STATE() = 1 -- transaction is active
ROLLBACK TRAN @TranName; -- execute original code
ELSE IF XACT_STATE() = -1 -- transaction is doomed; cannot be partially rolled back
ROLLBACK; -- fully roll back
IF (@@TRANCOUNT = 0)
BEGIN TRAN; -- restart transaction to fulfill expectations below
初步测试看起来不错。敬请关注。(在我对这个提议的编辑更有信心之后,我会提交给git。)
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