巨大的減速C＃存儲過程調用，參數嗅探/優化問題？

Question

我有以下代碼重複運行存儲過程。當我逐字運行SQL語句時，它工作得很好，所以我創建了一個存儲過程，它封裝了我正在做的事情。

foreach (string worker in workers) 
{ 
    _gzClasses.ExecuteCommand("EXEC dbo.Session_Aggregate @workerId = {0}, @timeThresh = {1}", worker, SecondThreshold); 
    Console.WriteLine("Inserted sessions for {0}", worker); 
} 

然後，我想知道每個呼叫有多少行產生，所以我改變了SP略微返回@@rowcount作爲輸出參數。我can't use the DataContext to execute commands with output parameters，所以我不得不改變內部的上述代碼迴路以下幾點：

using (var cn = new SqlConnection(CnStr)) 
{ 
    cn.Open(); 
    using (var cmd = new SqlCommand("Session_Aggregate", 
     cn) {CommandTimeout = 300}) 
    {       
     cmd.CommandType = CommandType.StoredProcedure;       

     cmd.Parameters.AddWithValue("@workerId", worker);       
     cmd.Parameters.AddWithValue("@timeThresh", SecondThreshold);       

     SqlParameter sessions = cmd.Parameters.Add("@sessions", SqlDbType.Int); 
     sessions.Direction = ParameterDirection.Output; 

     cmd.ExecuteNonQuery(); 

     Console.WriteLine("Inserted {1} sessions for {0}", worker, sessions.Value); 
    } 
} 

這工作，但它運行要比其他查詢慢。我認爲這可能是參數嗅探的一種情況，所以我將其更改爲CommandType.Text並使用字符串EXEC Session_Aggregate ... WITH RECOMPILE。但在這種情況下，我一直收到出錯參數@session未定義的錯誤。在任何情況下，即使SQL命令在1秒內在SSMS中運行<，現在查詢幾乎不運行。

這裏是存儲過程，以防萬一任何人都可以幫忙弄清楚發生了什麼，或者可以找出加快速度的方法。我也會指導如何正確描述這裏發生的事情。與CommandType.StoredProcedure我什至不能看到由VS發送到SQL的實際命令。

PROCEDURE [dbo].[Session_Aggregate] 
    -- Add the parameters for the stored procedure here 
    @workerId varchar(64) = 0, 
    @timeThresh dateTime = '13 July 2007 11:27:46' 
    @sessions INT OUTPUT 
AS 
BEGIN 
    -- SET NOCOUNT ON added to prevent extra result sets from 
    -- interfering with SELECT statements. 
    SET NOCOUNT ON; 

    -- Insert statements for procedure here 
    INSERT INTO e_activeSessions 
    SELECT * 
    FROM (
     SELECT workerId, startTime, COUNT(*) as totalTasks, MAX(timeInSession) as totalTime, 
     MIN(dwellTime) as minDwell, MAX(dwellTime) as maxDwell, AVG(dwellTime) as avgDwell, STDEV(dwellTime) as stdevDwell, 
     SUM(CAST(wrong80 as INT)) + SUM(CAST(correct80 as INT)) as total80, SUM(CAST(correct80 as INT)) as correct80, 
     SUM(CAST(correct80 as FLOAT))/NULLIF(SUM(CAST(wrong80 as INT)) + SUM(CAST(correct80 as INT)), 0) as percent80 
     FROM (
      SELECT *, (SELECT MAX(timeStamp) 
       FROM workerLog w where dwellTime is null AND timeInSession = 0 AND workerId = @workerId AND w.timeStamp <= workerLog.timeStamp 
        AND w.timeStamp >= @timeThresh) as startTime 
      FROM workerLog where workerId = @workerId) t 
    GROUP BY startTime, workerId) f 
    WHERE startTime is NOT NULL AND f.totalTasks > 1 AND totalTime > 0; 

    SET @sessions = @@ROWCOUNT; 
END 

編輯：不管原始查詢的執行計劃的，它是由創建臨時表加速顯著。我以爲SQL會通過分析查詢來完成這項工作，但我可能是錯的。 另外，我發現了OPTIMIZE FOR UNKNOWN提示，它在新版本的SQL Server中減輕了執行計劃針對大量不同數據大小時參數嗅探的影響。

PROCEDURE [dbo].[Session_Aggregate] 
    -- Add the parameters for the stored procedure here 
    @workerId varchar(64) = 0, 
    @timeThresh dateTime = '13 July 2007 11:27:46', 
    @sessions INT OUTPUT 
AS 
BEGIN 
    -- SET NOCOUNT ON added to prevent extra result sets from 
    -- interfering with SELECT statements. 
    SET NOCOUNT ON; 

    -- Insert statements for procedure here 

    CREATE TABLE #startTimes 
    (
     startTime DATETIME 
    ); 

    CREATE INDEX Idx_startTime ON #startTimes(startTime); 

    INSERT INTO #startTimes 
    SELECT timeStamp FROM workerLog 
    WHERE dwellTime is null AND timeInSession = 0 
    AND workerId = @workerId AND timeStamp >= @timeThresh; 

    INSERT INTO e_activeSessions 
    SELECT * 
    FROM (
     SELECT workerId, startTime, COUNT(*) as totalTasks, MAX(timeInSession) as totalTime, 
     MIN(dwellTime) as minDwell, MAX(dwellTime) as maxDwell, AVG(dwellTime) as avgDwell, STDEV(dwellTime) as stdevDwell, 
     SUM(CAST(wrong80 as INT)) + SUM(CAST(correct80 as INT)) as total80, SUM(CAST(correct80 as INT)) as correct80, 
     SUM(CAST(correct80 as FLOAT))/NULLIF(SUM(CAST(wrong80 as INT)) + SUM(CAST(correct80 as INT)), 0) as percent80 
     FROM (
      SELECT *, (SELECT MAX(startTime) FROM #startTimes where startTime <= workerLog.timeStamp) as startTime 
      FROM workerLog where workerId = @workerId) t 
    GROUP BY startTime, workerId) f 
    WHERE startTime is NOT NULL AND f.totalTasks > 1 AND totalTime > 0 
    OPTION (OPTIMIZE FOR UNKNOWN); 

    SET @sessions = @@ROWCOUNT;  
END; 

附加簡化：拖動SP到你的DBML文件，你可以做到以下幾點：

foreach (string worker in workers) 
{ 
    int? rows = 0; 
    _gzClasses.Session_Aggregate(worker, SecondThreshold, ref rows); 

    Console.WriteLine("Inserted {1} sessions for {0}", worker, rows); 
} 

Answer 1

火起來SQLServerProfiler，並且可以給你單查詢和之間的區別你現在正在運行它的方式。

http://www.techrepublic.com/article/step-by-step-an-introduction-to-sql-server-profiler/5054787

但更重要的是你應該看看，你可以通過查詢瓷磚和選擇顯示的執行計劃，SSMS打開查詢執行計劃。

http://www.mssqltips.com/sqlservertip/1856/sql-server-query-execution-plans-in-sql-server-management-studio/

如果你是真正的新SSMS我可能會看一對夫婦對我提供什麼上面的文章，但查詢執行計劃真的會告訴你在哪裏查詢滯後。 （基本的經驗法則是你不希望全表掃描發生，你希望它做的是尋找，這意味着你希望它在索引和/或主鍵上搜索）我不是dba，但那是在調試查詢時你可能想要採取的路線。

我不太確定這是您的查詢後，雖然審查，因爲它看起來很簡單。它可能與你調用它的次數有關。您可能想要找出一種方法將所有工作人員數據傳遞到查詢中，以便您只運行一次查詢本身，然後運行它。workers.count次......HTH