Query takes too long to run, how to optimize it? - sql

Question

The query structure: Helper-select in "with" clause - selects most recent entry using 'top 1 transaction_date'. Then does many joins. It takes too much time to run - what am I doing wrong?
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

There are a lot of things that does not seems good. First of all, your base query must be a lot simpler. Something like this:
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
For example, you are joining the DWH.DimWarehouseLotNumber but you are not extracting columns - do you really need it? Also, there are other columns which are not returned by the view - why to query them?
From, there you are first filtering by date and then y other fields, so your first TOP 20 records may be filtered by the next conditions - is this a behavior you want?
Also, do you really want this cast?
ON CAST(iioh.UnitOfMeasureKey AS VARCHAR(100)) = uom.UNIT_OF_MEASURE_PHK
It's better to use CONVERT, not FORMAT in performance aspect. Also, why not saving/materializing the TRANSACTION_DATE as INT (for example using a persisted computed column or just on CRUD) instead of calculating this value on each read?
Filtering by location code using LIKE clause can heart the performance, too. Why not adding a new column WareHouseLocationCodeType and set a same value for all locations satisfying this condition:
(wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')
Then you can filter by this column in the view since this is very important for you. Also, you can create filter index on this column to increase the performance, more.
Also, you may want to create a inline-function instead a view and pass the date as parameter:
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
)
Then call it like this:
SELECT TOP 20 *
FROM [IRWSMCMaterialization].[FactInventoryItemOnHandDailyView] ('2020-12-04')
ORDER BY #TRANSACTION_DATE DESC

Answer 2

The query optimization is science today. If you want to find bottlenecks in your query you can follow some of these steps:
As the first step, enable statistics with these commands:
SET STATISTICS TIME ON;
SET STATISTICS IO ON;
Once you execute these commands in some query windows in the same window execute your query. When your query is executed switch to the Messages tab and you will see a lot of useful information like TIME execution, parse and compile-time and maybe the most interesting I/O reads.
As the second step, try to understand which table has a lot of reads, for example if you are expecting 10 rows from the query, but in some tables you have 10k or 100k logical reads something is wrong. That means for the 10 rows query execution from one table reads 10k pages. Obviously you are missing some index on this table, try to find which index you need.
If you are having some static values in where clause like the following one, then think about Filtered Index:
bp.BRANCH_PLANT_CODE = '96100' AND iioh.QuantityOnHand > 0
Not always, but in some cases conversion can break your indexes if you are casting them or using some other function in where clause like the following one, even you have an index on this column query optimizer will not use it in query execution:
CAST(iioh.UnitOfMeasureKey AS VARCHAR(100))
The last one, if you have OR logical operator in your query try to execute one by one part of your OR logical operator separately see to performance. This logical operator can really kill your query, and this is one example:
AND (wloc.WAREHOUSE_LOCATION_CODE like '6000W01%' OR wloc.WAREHOUSE_LOCATION_CODE like 'BL%')
Once, you determine here that you don't have any issues you can go more further.