sql - 使用 TABLOCK、XLOCK 命令在 Microsoft SQL Server 2008 上出现间歇性死锁

Question

我遇到以下存储过程的间歇性死锁。它每分钟运行一次。它已经投入生产超过 1 年，我们通常不会收到此错误，但它有时会突然出现......在我们的一个环境中每天抛出 3 到 5 次异常......它与其他实例的环境相同没有抛出错误。存储过程被制作成一次只能运行一次，但也许我们这样做的方式不正确？

这里是错误:

System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.Data.SqlClient.SqlException: Transaction (Process ID 60) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

存储过程如下:

 SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[requestUpdate]
AS
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

BEGIN TRAN
    DECLARE @StartDate datetime,
            @EndDate datetime,
            @Throttle bit,
            @Expired bit

    SELECT @Throttle = 0
    SELECT @Expired = 0

    SELECT TOP 1 @StartDate = uq.StartDate, @EndDate = uq.EndDate
      FROM UpdateQueue uq WITH(TABLOCK,XLOCK)
     ORDER BY ID DESC

    -- PREVENT ANOTHER REQUEST IF THIS SP HAS BEEN
    -- CALLED IN THE LAST FORTY SECONDS.
    IF DATEADD(SECOND,-40,GETDATE()) < @StartDate
    BEGIN
      SELECT @Throttle = 1
    END

    -- CREATE ANOTHER REQUEST IF THE CURRENT ONE
    -- HAS NOT COMPLETED IN THE LAST FIVE MINUTES.
    IF @StartDate <= DATEADD(MINUTE,-5,GETDATE())
    BEGIN
      SELECT @Expired = 1
    END

    -- HAS THE CURRENT REQUEST EXPIRED?
    IF @EndDate IS NULL AND @Expired = 1
    BEGIN
      INSERT INTO UpdateQueue (RequestID, StartDate) OUTPUT 'EXPIRED' AS Result, INSERTED.RequestID AS RequestID
      VALUES (NEWID(), GETDATE())
    END

    -- HAS THE CURRENT REQUEST COMPLETED AND YOU ARE NOT THROTTLING
    -- OR HAVE THERE NOT BEEN ANY REQUESTS YET?
    ELSE IF (@EndDate IS NOT NULL AND @Throttle = 0) OR @StartDate IS NULL
    BEGIN
      INSERT INTO UpdateQueue (RequestID, StartDate) OUTPUT 'STARTED' AS Result, INSERTED.RequestID AS RequestID
      VALUES (NEWID(), GETDATE())
    END

    -- Running
    ELSE
    BEGIN
      SELECT 'RUNNING' AS Result, NULL AS RequestID
    END

COMMIT

Answer 1

我怀疑这是某个特定锁的持有时间超过了您的连接愿意等待的时间。如果没有什么可以终止长时间运行的事务，在这里，您将遇到这种情况，因为当连接超时时，SQL Server 会强制等待结束并终止作为死锁受害者的传入锁。

长话短说:一些进程(不是这里详述的)正在锁定表，导致死锁。

检查当您遇到死锁时还发生了什么 - 是否有备份正在运行，或者其他什么东西锁定了这个表？