查询运行时间过长，如何优化？

Question

查询结构：“with”子句中的 Helper-select - 使用“top 1 transaction_date”选择最近的条目。然后做很多连接。运行时间太长 - 我做错了什么？

CREATE VIEW [IRWSMCMaterialization].[FactInventoryItemOnHandDailyView] AS
WITH TempTBLFactIvnItmDaily AS (
SELECT TOP 20
     ITEM_NUMBER AS [InventoryItemNumber]
    ,CAST(FORMAT(TRANSACTION_DATE, 'yyyyMMdd') AS INT) AS [DateKey]
    ,BRANCH_PLANT_FHK AS [BranchPlantKey]
    ,BRANCH_PLANT_CODE AS [BranchPlantCode]
    ,CAST(QUANTITY_ON_HAND AS BIGINT)  AS [QuantityOnHand]
    ,TRANSACTION_DATE AS [Date]
    ,WAREHOUSE_LOCATION_FHK AS [WarehouseLocationKey]
    ,WAREHOUSE_LOCATION_CODE AS [WarehouseLocationCode]
    ,WAREHOUSE_LOT_NUMBER_CODE  AS [WarehouseLotNumber]
    ,WAREHOUSE_LOT_NUMBER_FHK AS [WarehouseLotNumberKey]
    ,UNIT_OF_MEASURE AS [UnitOfMeasureName]
    ,UNIT_OF_MEASURE_PHK AS [UnitOfMeasureKey]
    
  FROM dbo.RS_INV_ITEM_ON_HAND
-- below is where clause, choose only most recent entry
WHERE TRANSACTION_DATE = (SELECT TOP 1 TRANSACTION_DATE FROM dbo.RS_INV_ITEM_ON_HAND ORDER BY TRANSACTION_DATE DESC)
)

SELECT [InventoryItemNumber],
                [DateKey],
                [Date],
                [BranchPlantCode] AS [BP],
                [WarehouseLocationCode] AS [Location],
                [QuantityOnHand],
                [UnitOfMeasureName] AS [UoM],
                CASE [WarehouseLotNumber]
                 WHEN 'Not Assigned' THEN NULL
                ELSE [WarehouseLotNumber]
                  END
                AS [Lot]
FROM TempTBLFactIvnItmDaily iioh
JOIN DWH.DimBranchPlant bp ON  iioh.BranchPlantKey = bp.BRANCH_PLANT_PHK
JOIN DWH.DimWarehouseLocation wloc ON iioh.WarehouseLocationKey = wloc.WAREHOUSE_LOCATION_PHK
JOIN DWH.DimWarehouseLotNumber wlot ON iioh.WarehouseLotNumberKey = wlot.WarehouseLotNumber_PHK
JOIN DWH.DimUnitOfMeasure uom ON CAST(iioh.UnitOfMeasureKey AS VARCHAR(100)) = uom.UNIT_OF_MEASURE_PHK
where bp.BRANCH_PLANT_CODE = '96100' 
    AND iioh.QuantityOnHand > 0
    AND (wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')
GO

Answer 1

有很多事情看起来并不好。首先，您的基本查询必须简单得多。像这样的：

SELECT iioh.ITEM_NUMBER AS [InventoryItemNumber],
       CAST(FORMAT(iioh.TRANSACTION_DATE, 'yyyyMMdd') AS INT) AS [DateKey],
       iioh.TRANSACTION_DATE AS [Date],
       iioh.BRANCH_PLANT_CODE AS [BP],
       iioh.WAREHOUSE_LOCATION_CODE AS [Location],
       CAST(iioh.QUANTITY_ON_HAND AS BIGINT) AS [QuantityOnHand],
       iioh.UNIT_OF_MEASURE AS [UoM],
       NULLIF(iioh.WAREHOUSE_LOT_NUMBER_CODE, 'Not Assigned') AS [Lot]        
FROM dbo.RS_INV_ITEM_ON_HAND iioh
JOIN DWH.DimBranchPlant bp 
    ON  iioh.BranchPlantKey = bp.BRANCH_PLANT_PHK
JOIN DWH.DimWarehouseLocation wloc 
    ON iioh.WarehouseLocationKey = wloc.WAREHOUSE_LOCATION_PHK
JOIN DWH.DimUnitOfMeasure uom 
    ON CAST(iioh.UnitOfMeasureKey AS VARCHAR(100)) = uom.UNIT_OF_MEASURE_PHK
where bp.BRANCH_PLANT_CODE = '96100' 
    AND iioh.QuantityOnHand > 0
    AND (wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')
    AND iioh.TRANSACTION_DATE = @TRANSACTION_DATE

例如，您正在加入DWH.DimWarehouseLotNumber，但您没有提取列 - 您真的需要它吗？此外，视图未返回其他列 - 为什么要查询它们？

从那里，您首先按 date 过滤，然后是 y 其他字段，因此您的前 20 条记录可能会按下一个条件过滤 - 这是您想要的行为吗？

另外，你真的想要这个演员吗？

ON CAST(iioh.UnitOfMeasureKey AS VARCHAR(100)) = uom.UNIT_OF_MEASURE_PHK

在性能方面最好使用CONVERT，而不是FORMAT。另外，为什么不将 TRANSACTION_DATE 保存/具体化为 INT（例如使用持久计算列或仅在 CRUD 上），而不是在每次读取时计算此值？

使用LIKE 子句过滤location code 也可以提高性能。为什么不添加一个新列 WareHouseLocationCodeType 并为所有满足此条件的位置设置相同的值：

(wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')

然后您可以在视图中按此列进行过滤，因为这对您非常重要。此外，您可以在此列上创建filter index 以提高性能等等。

此外，您可能希望创建一个内联函数而不是视图并将日期作为参数传递：

CREATE OR ALTER FUNCTION [IRWSMCMaterialization].[FactInventoryItemOnHandDailyView] 
(
    @TRANSACTION_DATE datetime
)
RETURNS TABLE
AS
RETURN
(
    SELECT iioh.ITEM_NUMBER AS [InventoryItemNumber],
           CAST(FORMAT(iioh.TRANSACTION_DATE, 'yyyyMMdd') AS INT) AS [DateKey],
           iioh.TRANSACTION_DATE AS [Date],
           iioh.BRANCH_PLANT_CODE AS [BP],
           iioh.WAREHOUSE_LOCATION_CODE AS [Location],
           CAST(iioh.QUANTITY_ON_HAND AS BIGINT) AS [QuantityOnHand],
           iioh.UNIT_OF_MEASURE AS [UoM],
           NULLIF(iioh.WAREHOUSE_LOT_NUMBER_CODE, 'Not Assigned') AS [Lot]  
          ,iioh.TRANSACTION_DATE 
    FROM dbo.RS_INV_ITEM_ON_HAND iioh
    JOIN DWH.DimBranchPlant bp 
        ON  iioh.BranchPlantKey = bp.BRANCH_PLANT_PHK
    JOIN DWH.DimWarehouseLocation wloc 
        ON iioh.WarehouseLocationKey = wloc.WAREHOUSE_LOCATION_PHK
    JOIN DWH.DimUnitOfMeasure uom 
        ON CAST(iioh.UnitOfMeasureKey AS VARCHAR(100)) = uom.UNIT_OF_MEASURE_PHK
    where bp.BRANCH_PLANT_CODE = '96100' 
        AND iioh.QuantityOnHand > 0
        AND (wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')
        AND iioh.TRANSACTION_DATE = @TRANSACTION_DATE
)

然后这样称呼它：

SELECT TOP 20 *
FROM [IRWSMCMaterialization].[FactInventoryItemOnHandDailyView] ('2020-12-04')
ORDER BY @TRANSACTION_DATE DESC

Answer 2

查询优化是当今的科学。如果您想在查询中找到瓶颈，可以按照以下步骤操作：

第一步，使用以下命令启用统计信息：

SET STATISTICS TIME ON;
SET STATISTICS IO ON;

一旦您在同一窗口的某些查询窗口中执行这些命令，就会执行您的查询。执行查询时切换到Messages 选项卡，您将看到很多有用的信息，例如执行时间、解析和编译时间，可能还有最有趣的 I/O 读取。

作为第二步，尝试了解哪个表有大量读取，例如，如果您期望查询中有 10 行，但在某些表中您有 10k 或 100k 逻辑读取，则出现问题。这意味着从一个表执行 10 行查询会读取 10k 页。显然你在这张表上缺少一些索引，试着找到你需要的索引。

如果您在 where 子句中有一些静态值，如下所示，请考虑 Filtered Index：

bp.BRANCH_PLANT_CODE = '96100' AND iioh.QuantityOnHand > 0

并非总是如此，但在某些情况下，如果您在转换索引或在 where 子句中使用其他函数（如下所示），转换可能会破坏您的索引，即使您在此列上有索引，查询优化器也不会在查询执行中使用它：

CAST(iioh.UnitOfMeasureKey AS VARCHAR(100))

最后一个，如果您的查询中有OR 逻辑运算符，请尝试逐个执行OR 逻辑运算符的一部分，分别查看性能。这个逻辑运算符真的可以杀死你的查询，这是一个例子：

AND (wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')

一旦你在这里确定你没有任何问题，你可以走得更远。