高效交易，记录锁定

我有一个存储过程，它选择1记录回来。存储过程可以从不同的PC上的几个不同的应用程序调用。这个想法是，存储过程带回需要处理的下一条记录，并且如果两个应用程序同时调用存储过程，则不应该返回相同的记录。我的查询在下面，我试图尽可能高效地编写查询（SQL 2008）。它能比这更有效地完成吗？高效交易，记录锁定

CREATE PROCEDURE GetNextUnprocessedRecord 
AS 
BEGIN 
    SET NOCOUNT ON; 

    --ID of record we want to select back 
    DECLARE @iID BIGINT  

    -- Find the next processable record, and mark it as dispatched 
    -- Must be done in a transaction to ensure no other query can get 
    -- this record between the read and update 
    BEGIN TRAN 

     SELECT TOP 1 
      @iID = [ID] 
     FROM 
      --Don't read locked records, only lock the specific record 
      [MyRecords] WITH (READPAST, ROWLOCK) 
     WHERE 
      [Dispatched] is null 
     ORDER BY 
      [Received] 

     --Mark record as picked up for processing 
     UPDATE 
      [MyRecords] 
     SET 
      [Dispatched] = GETDATE() 
     WHERE 
      [ID] = @iID  

    COMMIT TRAN 

    --Select back the specific record 
    SELECT 
     [ID], 
     [Data] 
    FROM  
     [MyRecords] WITH (NOLOCK, READPAST) 
    WHERE 
     [ID] = @iID 

END

来源

2009-02-22 Jeremy

我不相信这个TSQL是事务安全... – 2009-02-22 08:07:45

尝试把一个WAITFOR DELAY“0：2：0”后的SELECT和UPDATE之前，运行SP，并从另一个连接实际执行同一SP ... – 2009-02-22 08:17:24

，我错了！ HOLDLOCK与MyRecords表上的REPEATABLEREAD具有相同的效果。 – 2009-02-22 08:22:27

使用READPAST锁定提示是正确的，你的SQL看起来不错。

我想补充使用XLOCK虽然这也是HOLDLOCK/SERIALIZABLE

... 
[MyRecords] WITH (READPAST, ROWLOCK, XLOCK) 
...

这意味着你的ID，虽然你坚持下去，并更新其独占锁定该行。

编辑：在调度和接收列添加一个索引，使之更快。如果[ID]（我认为它是PK）未被聚类，INCLUDE [ID]。和过滤指数也因为它是SQL 2008

你也可以使用这个结构，它所有这一切一气呵成，不XLOCK或HOLDLOCK

UPDATE 
    MyRecords 
SET 
    --record the row ID 
    @id = [ID], 
    --flag doing stuff 
    [Dispatched] = GETDATE() 
WHERE 
    [ID] = (SELECT TOP 1 [ID] FROM MyRecords WITH (ROWLOCK, READPAST) WHERE Dispatched IS NULL ORDER BY Received)

UPDATE, assign, set in one

来源

2009-02-22 16:08:32 gbn