SQL Server优化技巧之SQL Server中的"MapReduce"

日常的OLTP环境中,有时会涉及到一些统计方面的SQL语句,这些语句可能消耗巨大,进而影响整体运行环境,这里我为大家介绍如何利用SQL Server中的”类MapReduce”方式,在特定的统计情形中不牺牲响应速度的情形下减少资源消耗.

我们可能经常会利用开窗函数对巨大的数据集进行分组统计排序.比如下面的例子:

脚本环境

/*
This script creates two new tables in AdventureWorks:

dbo.bigProduct
dbo.bigTransactionHistory
*/


USE AdventureWorks
GO

SELECT
    p.ProductID + (a.number * 1000) AS ProductID,
    p.Name + CONVERT(VARCHAR, (a.number * 1000)) AS Name,
    p.ProductNumber + '-' + CONVERT(VARCHAR, (a.number * 1000)) AS ProductNumber,
    p.MakeFlag,
    p.FinishedGoodsFlag,
    p.Color,
    p.SafetyStockLevel,
    p.ReorderPoint,
    p.StandardCost,
    p.ListPrice,
    p.Size,
    p.SizeUnitMeasureCode,
    p.WeightUnitMeasureCode,
    p.Weight,
    p.DaysToManufacture,
    p.ProductLine,
    p.Class,
    p.Style,
    p.ProductSubcategoryID,
    p.ProductModelID,
    p.SellStartDate,
    p.SellEndDate,
    p.DiscontinuedDate
INTO bigProduct
FROM Production.Product AS p
CROSS JOIN master..spt_values AS a
WHERE
    a.type = 'p'
    AND a.number BETWEEN 1 AND 50
GO


ALTER TABLE bigProduct
ALTER COLUMN ProductId INT NOT NULL    
GO

ALTER TABLE bigProduct
ADD CONSTRAINT pk_bigProduct PRIMARY KEY (ProductId)
GO


SELECT 
    ROW_NUMBER() OVER 
    (
        ORDER BY 
            x.TransactionDate,
            (SELECT NEWID())
    ) AS TransactionID,
    p1.ProductID,
    x.TransactionDate,
    x.Quantity,
    CONVERT(MONEY, p1.ListPrice * x.Quantity * RAND(CHECKSUM(NEWID())) * 2) AS ActualCost
INTO bigTransactionHistory
FROM
(
    SELECT
        p.ProductID, 
        p.ListPrice,
        CASE
            WHEN p.productid % 26 = 0 THEN 26
            WHEN p.productid % 25 = 0 THEN 25
            WHEN p.productid % 24 = 0 THEN 24
            WHEN p.productid % 23 = 0 THEN 23
            WHEN p.productid % 22 = 0 THEN 22
            WHEN p.productid % 21 = 0 THEN 21
            WHEN p.productid % 20 = 0 THEN 20
            WHEN p.productid % 19 = 0 THEN 19
            WHEN p.productid % 18 = 0 THEN 18
            WHEN p.productid % 17 = 0 THEN 17
            WHEN p.productid % 16 = 0 THEN 16
            WHEN p.productid % 15 = 0 THEN 15
            WHEN p.productid % 14 = 0 THEN 14
            WHEN p.productid % 13 = 0 THEN 13
            WHEN p.productid % 12 = 0 THEN 12
            WHEN p.productid % 11 = 0 THEN 11
            WHEN p.productid % 10 = 0 THEN 10
            WHEN p.productid % 9 = 0 THEN 9
            WHEN p.productid % 8 = 0 THEN 8
            WHEN p.productid % 7 = 0 THEN 7
            WHEN p.productid % 6 = 0 THEN 6
            WHEN p.productid % 5 = 0 THEN 5
            WHEN p.productid % 4 = 0 THEN 4
            WHEN p.productid % 3 = 0 THEN 3
            WHEN p.productid % 2 = 0 THEN 2
            ELSE 1 
        END AS ProductGroup
    FROM bigproduct p
) AS p1
CROSS APPLY
(
    SELECT
        transactionDate,
        CONVERT(INT, (RAND(CHECKSUM(NEWID())) * 100) + 1) AS Quantity
    FROM
    (
        SELECT 
            DATEADD(dd, number, '20050101') AS transactionDate,
            NTILE(p1.ProductGroup) OVER 
            (
                ORDER BY number
            ) AS groupRange
        FROM master..spt_values
        WHERE 
            type = 'p'
    ) AS z
    WHERE
        z.groupRange % 2 = 1
) AS x



ALTER TABLE bigTransactionHistory
ALTER COLUMN TransactionID INT NOT NULL
GO


ALTER TABLE bigTransactionHistory
ADD CONSTRAINT pk_bigTransactionHistory PRIMARY KEY (TransactionID)
GO


CREATE NONCLUSTERED INDEX IX_ProductId_TransactionDate
ON bigTransactionHistory
(
    ProductId,
    TransactionDate
)
INCLUDE 
(
    Quantity,
    ActualCost
)
GO

View Code