Question

我已获得最新的SQL 2012标准版：

Microsoft SQL Server 2012（SP3-CU3）（KB3152635） - 11.0.6537.0（X64） 2016年4月28日17:57:34版权所有（c）Microsoft Corporation Standard Windows NT 6.1上的版本（64位）（Build 7601：Service Pack 1）（管理程序）

在基于每个客户的用户数量的2个变量（月份和年份）的简单计数中，应用程序是特定的用户，行估计值是实际结果的10倍。我已经释放了缓存，重建了索引，确保它正在进行索引查找并尝试重新编译计划。如果我手动输入谓词，我会得到预期的结果和计划，但如果我使用dateadd，我会得到一个版本，因为我在使用CTE的视图中有多个计数，我希望找到一个方法我相信dateadd正在造成大量的行数估计。

    SELECT
    [Customer],
    [Month],
    [Year],
    COUNT([Username]) AS 'RDS'
    FROM [MS_CitrixUsers]
    WHERE [Application] = 'RDS'
    AND [Month] = DATENAME(month, dateadd(month, -1,GETDATE()))
    AND [YEAR] = DATENAME(year, dateadd(month, -1,GETDATE()))
    GROUP BY [MS_CitrixUsers].[Customer],
    [MS_CitrixUsers].[Month],
    [MS_CitrixUsers].[Year]

计数在包含膨胀行数的排序后触发流聚合。

Plan

Stream Properties

我的观点如下：

    WITH RDS1 
    AS
    (
    SELECT
    [Customer],
    COUNT([Username]) AS 'RDS1'
    FROM [MS_CitrixUsers]
    WHERE [Application] = 'RDS'
    AND [Month] = @month 
    AND [YEAR] = @year
    GROUP BY [MS_CitrixUsers].[Customer],
    [MS_CitrixUsers].[Month],
    [MS_CitrixUsers].[Year]
    ),
    RDS2 
    AS
    (
    SELECT
    [Customer],
    [Month],
    [Year],
    COUNT([Username]) AS 'RDS2'
    FROM [MS_CitrixUsers]
    WHERE [Application] = 'RDS'
    AND [Month] = @monthbefore
    AND [YEAR] = @year2
    GROUP BY [MS_CitrixUsers].[Customer],
    [MS_CitrixUsers].[Month],
    [MS_CitrixUsers].[Year]
    ),
    ...

    SELECT c.Customer,
    CASE WHEN NOT EXISTS (SELECT [RDS1] FROM [RDS1] t1 WHERE t1.Customer =     c.Customer) 
AND EXISTS (SELECT [RDS2] FROM [RDS2] t2 WHERE t2.Customer = c.Customer) THEN '99999' ELSE ([RDS1] - Coalesce([RDS2], 0)) END AS 'RDS',
CASE WHEN NOT EXISTS (SELECT [CitrixUsage1] FROM [CitrixUsage] t1 WHERE t1.Customer = c.Customer) 
AND EXISTS (SELECT [CitrixUsage2] FROM [CitrixUsage2] t2 WHERE t2.Customer = c.Customer) THEN '99999' ELSE ([CitrixUsage1] - Coalesce([CitrixUsage2], 0)) END    AS 'Citrix Usage',

我得到的预期结果是两个月的数据差异：

[客户] [application1] ... [applicationN]

Customer1 -1 3

我们有相当多的应用程序，因此您可以想象返回结果需要相当长的时间，所以我看到优化估算值是否会有所帮助。

解决方法：我发现在这里的另一个答案是，使用临时表，将变量放在那里，并加入我的表，避免了流聚合，并使用哈希匹配来估计正确行数。

Answer 1

你应该尽量不在谓词中计算。你没有提到这是否是一个视图，但你不能声明变量;

DECLARE @MonthVariable varchar(10); SET @MonthVariable = DATENAME(month, dateadd(month, -1,GETDATE()))
DECLARE @YearVariable int; SET @YearVariable = DATENAME(year, dateadd(month, -1,GETDATE()))

SELECT
    [Customer],
    [Month],
    [Year],
    COUNT([Username]) AS 'RDS'
FROM [MS_CitrixUsers]
WHERE [Application] = 'RDS'
    AND [Month] = @MonthVariable
    AND [YEAR] = @YearVariable
GROUP BY [MS_CitrixUsers].[Customer],
    [MS_CitrixUsers].[Month],
    [MS_CitrixUsers].[Year]

所以这是一个观点，试试这个;

SELECT
    [Customer],
    [Month],
    [Year],
    COUNT([Username]) AS 'RDS'
FROM [MS_CitrixUsers] a
INNER JOIN (SELECT
             DATENAME(month, dateadd(month, -1,GETDATE())) CurMon
            ,DATENAME(year, dateadd(month, -1,GETDATE())) CurYear
            ) b
    ON a.[Month] = b.CurMon
    AND a.[Year] = b.CurYear
WHERE [Application] = 'RDS'
GROUP BY [MS_CitrixUsers].[Customer],
    [MS_CitrixUsers].[Month],
     [MS_CitrixUsers].[Year]

Answer 2

我的解决方法版本：

CREATE TABLE #MasterDate( [Month1] varchar(50), [YEAR1] varchar(10),[Month2] varchar(50),[YEAR2] varchar(10))
INSERT INTO #MasterDate ([Month1],[YEAR1],[Month2],[YEAR2] )
    SELECT DATENAME(month, dateadd(month, -1,GETDATE())) 
    ,DATENAME(year, dateadd(month, -1,GETDATE()))
    ,DATENAME(month, dateadd(month, -2,GETDATE())) 
    ,DATENAME(year, dateadd(month, -2,GETDATE()))

;WITH RDS1 
AS
(
SELECT
[Customer]
,[MS_CitrixUsers].[Month]
,[MS_CitrixUsers].[YEAR]
,COUNT([Username]) AS 'RDS1'
FROM [MS_CitrixUsers]
INNER JOIN #MasterDate m ON [Month] = m.[Month1] and [YEAR] = m.[YEAR1]
WHERE [Application] = 'RDS'
GROUP BY [MS_CitrixUsers].[Customer],
[MS_CitrixUsers].[Month],
[MS_CitrixUsers].[Year]
),

RDS2 
AS
(
SELECT
[Customer],
[Month],
[Year],
COUNT([Username]) AS 'RDS2'
FROM [MS_CitrixUsers]
INNER JOIN #MasterDate m ON [Month] = m.[Month2] and [YEAR] = m.[YEAR2]
WHERE [Application] = 'RDS'
GROUP BY [MS_CitrixUsers].[Customer],
[MS_CitrixUsers].[Month],
[MS_CitrixUsers].[Year]
)
SELECT c.Customer,
CASE WHEN NOT EXISTS (SELECT [RDS1] FROM [RDS1] t1 WHERE t1.Customer = c.Customer) 
AND EXISTS (SELECT [RDS2] FROM [RDS2] t2 WHERE t2.Customer = c.Customer) THEN '99999' ELSE ([RDS1] - Coalesce([RDS2], 0)) END AS 'RDS'
FROM [Customers] c
INNER JOIN #MasterDate m ON [Month] = m.[Month2] and [YEAR] = m.[YEAR2]
LEFT JOIN RDS1 t1 ON t1.Customer = c.Customer
LEFT JOIN RDS2 t2 ON t2.Customer = c.Customer

DROP TABLE #MasterDate

当然，这不是一个视图，只有SP。现在的问题是，它是否解决了我的速度问题，只需另外50个cte进行编辑。

编辑：完成我的SP版本的视图，内部连接到#temp表而不是dateadd视图。

查看完成时间：37秒

SP：11秒。

SQL 2012 SP3 DATEADD谓词导致计数查询中的高估计

2 个答案: