功能的递归CTE似乎是很慢

Question

我目前工作中，我使用递归CTE的功能，但似乎都表现不佳。我需要这个功能（所以没有临时表），所以我可以很容易地在存储过程中使用它。

下面是代码：

CREATE FUNCTION [dbo].[Web_GetDailyLoadListUDF] 
(
    @CustomerID INT 
    , @StartDate DATETIME 
    , @Days INT 
    , @IncludeChildren BIT 
) 
RETURNS @TableOfValues TABLE 
( 
    RowID SMALLINT IDENTITY(1,1) 
    , DailyLoadCount INT 
    , DailyLoadDate VARCHAR(6) 
    , FullDate DATETIME 
) 
AS 
BEGIN 
    DECLARE @MaxDate DATETIME; 
    SET @MaxDate = DATEADD(dd, @Days * -1.7, DATEDIFF(dd, 0, @StartDate)); 

    WITH DateCTE AS 
    (
     SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @StartDate)) AS DateValue 
     UNION ALL 
     SELECT DATEADD(DAY, -1, DateValue) 
     FROM DateCTE 
     WHERE DATEADD(DAY, -1, DateValue) > @MaxDate 
    ) 
    INSERT INTO @TableOfValues 
    SELECT * FROM 
    (
     SELECT TOP (@Days) 
      (
       SELECT COUNT(*) 
       FROM dbo.[Load] l WITH (NOLOCK) 
       JOIN dbo.LoadCustomer lc WITH (NOLOCK) 
        ON lc.LoadID = l.ID 
       JOIN dbo.Customer c WITH (NOLOCK) 
        ON c.ID = lc.CustomerID 
       WHERE DATEADD(dd, 0, DATEDIFF(dd, 0, l.LoadDate)) = dct.DateValue 
        AND l.StateType = 1 
        AND lc.Main = 1 
        AND (c.ID = @CustomerID OR (@IncludeChildren = 1 AND c.ParentCustomerID = @CustomerID)) 
      ) AS DailyLoadCount 
      , CONVERT(VARCHAR(6), dct.DateValue, 107) AS DailyLoadDate 
      , dct.DateValue 
     FROM DateCTE dct 
     WHERE 
      DATEPART(DW, dct.DateValue) NOT IN (1, 7) 
      AND dct.DateValue NOT IN 
      (
       SELECT HolidayDate FROM Holiday 
      ) 
     ORDER BY dct.DateValue DESC 
    ) AS S 
    ORDER BY s.DateValue ASC 

    RETURN 
END 

---

什么这个SQL应该检索是每天负载的数量，在过去的@days是工作日（没有周末/节假日）。

我基本上只需要一些帮助优化这使得它不会跑这么慢。 （每位顾客花费20秒，这将被称为超过数千）。

Answer 1

你的主要问题是，就在这里

WHERE DATEADD(dd, 0, DATEDIFF(dd, 0, l.LoadDate)) = dct.DateValue 

应该

WHERE l.LoadDate >= dct.DateValue 
    AND l.LoadDate < dct.DateValue +1 

创建上载合成指数法（LoadDate，ID）和加载（ID，LoadDate）和下降，做了一个没有在查询计划中使用。

您应该显示查询计划，只要你是问有关的性能问题。要查看查询计划，请使用变量为输入参数自行在函数内运行查询。从SSMS菜单，启用选项“查询 - >包括实际的执行计划”

既然你没有足够的代表，发布图片，您可以按如下揭示文本计划。在第一个SELECT语句中提供一些合理的参数。

set showplan_text on; 

然后，在文本模式下，即，按下Ctrl-T，然后Ctrl-E运行的下方。

DECLARE  
     @CustomerID INT 
    , @StartDate DATETIME 
    , @Days INT 
    , @IncludeChildren BIT 

SELECT 
     @CustomerID = 1 
    , @StartDate = '20110201' 
    , @Days = 10 
    , @IncludeChildren = 1 

DECLARE @TableOfValues TABLE 
( 
    RowID SMALLINT IDENTITY(1,1) 
    , DailyLoadCount INT 
    , DailyLoadDate VARCHAR(6) 
    , FullDate DATETIME 
) 

    DECLARE @MaxDate DATETIME; 
    SET @MaxDate = DATEADD(dd, @Days * -1.7, DATEDIFF(dd, 0, @StartDate)); 

    WITH DateCTE AS 
    (
     SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @StartDate)) AS DateValue 
     UNION ALL 
     SELECT DATEADD(DAY, -1, DateValue) 
     FROM DateCTE 
     WHERE DATEADD(DAY, -1, DateValue) > @MaxDate 
    ) 
    INSERT INTO @TableOfValues 
    SELECT * FROM 
    (
     SELECT TOP (@Days) 
      (
       SELECT COUNT(*) 
       FROM dbo.[Load] l WITH (NOLOCK) 
       JOIN dbo.LoadCustomer lc WITH (NOLOCK) 
        ON lc.LoadID = l.ID 
       JOIN dbo.Customer c WITH (NOLOCK) 
        ON c.ID = lc.CustomerID 
       WHERE DATEADD(dd, 0, DATEDIFF(dd, 0, l.LoadDate)) = dct.DateValue 
        AND l.StateType = 1 
        AND lc.Main = 1 
        AND (c.ID = @CustomerID OR (@IncludeChildren = 1 AND c.ParentCustomerID = @CustomerID)) 
      ) AS DailyLoadCount 
      , CONVERT(VARCHAR(6), dct.DateValue, 107) AS DailyLoadDate 
      , dct.DateValue 
     FROM DateCTE dct 
     WHERE 
      DATEPART(DW, dct.DateValue) NOT IN (1, 7) 
      AND dct.DateValue NOT IN 
      (
       SELECT HolidayDate FROM Holiday 
      ) 
     ORDER BY dct.DateValue DESC 
    ) AS S 
    ORDER BY s.DateValue ASC 

SELECT * FROM @TableOfValues 

编辑计划到你的问题

Answer 2

您应该使用内联UDF代替（现在使用的是实际上是一个临时表） 见http://msdn.microsoft.com/en-us/library/ms189294.aspx

或将其转换成图代替。

Answer 3

相关子查询运行一行接一行，不使用它们。相反，使用连接或连接到派生表。您还需要确保where子句可以利用索引。在可疑的查询上搜索，看看哪些东西不能使用索引，以及如何使索引使用索引。