高效交易，記錄鎖定

我有一個存儲過程，它選擇1記錄回來。存儲過程可以從不同的PC上的幾個不同的應用程序調用。這個想法是，存儲過程帶回需要處理的下一條記錄，並且如果兩個應用程序同時調用存儲過程，則不應該返回相同的記錄。我的查詢在下面，我試圖儘可能高效地編寫查詢（SQL 2008）。它能比這更有效地完成嗎？高效交易，記錄鎖定

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

來源

2009-02-22 Jeremy

我不相信這個TSQL是事務安全... – 2009-02-22 08:07:45

嘗試把一個WAITFOR DELAY「0：2：0」後的SELECT和UPDATE之前，運行SP，並從另一個連接實際執行同一SP ... – 2009-02-22 08:17:24

，我錯了！ HOLDLOCK與MyRecords表上的REPEATABLEREAD具有相同的效果。 – 2009-02-22 08:22:27

使用READPAST鎖定提示是正確的，你的SQL看起來不錯。

我想補充使用XLOCK雖然這也是HOLDLOCK/SERIALIZABLE

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

這意味着你的ID，雖然你堅持下去，並更新其獨佔鎖定該行。

編輯：在調度和接收列添加一個索引，使之更快。如果[ID]（我認爲它是PK）未被聚類，INCLUDE [ID]。和過濾指數也因爲它是SQL 2008

你也可以使用這個結構，它所有這一切一氣呵成，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

來源

2009-02-22 16:08:32 gbn