Question

我有一个存储过程从表中读取并做出决策，每分钟调用一次。我有一种情况，在24小时内，每小时有3到5个请求失败。我想也许桌子被锁定了什么？这是我的存储过程。我是否需要具有隔离级别等的交易？这个想法是在查询运行时没有任何东西可以读取或写入该表。它应该是原子的。

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

GO

SQL查询TABLOCK和XLOCK超时，每5分钟一次，持续12小时以上

0 个答案: