Post on 01-Aug-2020
Grant Fritchey | www.ScaryDBA.com
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Reading Execution
Plans: The Deep Dive
for PASS Performance Virtual Chapter 4/26/12
Grant Fritchey
Grant Fritchey | www.ScaryDBA.com
Grant Fritchey
Product Evangelist for Red Gate Software
Twitter: @gfritchey
Blog: scarydba.com
Email: grant@scarydba.com
Grant Fritchey | www.ScaryDBA.com
A Query
SELECT soh.PurchaseOrderNumber, soh.AccountNumber, p.Name, sod.OrderQty, sod.LineTotal, cc.CardNumber FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail AS sod ON soh.SalesOrderID = sod.SalesOrderID JOIN Production.Product AS p ON sod.ProductID = p.ProductID JOIN Sales.CreditCard AS cc ON soh.CreditCardID = cc.CreditCardID
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A plan
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The Select Operator
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Clustered Index Scan
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Merge Join
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Hash Join
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The Pipe
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Compute Scalar
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An Entirely New Query
SELECT soh.PurchaseOrderNumber, soh.AccountNumber, p.Name, sod.OrderQty, sod.LineTotal, cc.CardNumber FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail AS sod ON soh.SalesOrderID = sod.SalesOrderID JOIN Production.Product AS p ON sod.ProductID = p.ProductID JOIN Sales.CreditCard AS cc ON soh.CreditCardID = cc.CreditCardID WHERE soh.CustomerID = 24624
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An Entirely New Query
SELECT soh.PurchaseOrderNumber, soh.AccountNumber, p.Name, sod.OrderQty, sod.LineTotal, cc.CardNumber FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail AS sod ON soh.SalesOrderID = sod.SalesOrderID JOIN Production.Product AS p ON sod.ProductID = p.ProductID JOIN Sales.CreditCard AS cc ON soh.CreditCardID = cc.CreditCardID WHERE soh.CustomerID = 24624
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A New Plan
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The Select Operator 2
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Index Seek
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Nested Loop Join
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Key Lookup
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Stored Procedure
IF (SELECT OBJECT_ID('spAddressByCity')
) IS NOT NULL
DROP PROCEDURE dbo.spAddressByCity ;
GO
CREATE PROC dbo.spAddressByCity @City NVARCHAR(30)
AS
SELECT a.AddressID,
a.AddressLine1,
a.AddressLine2,
a.City,
sp.[Name] AS StateProvinceName,
a.PostalCode
FROM Person.Address AS a
JOIN Person.StateProvince AS sp
ON a.StateProvinceID = sp.StateProvinceID
WHERE a.City = @City ;
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The Plan
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Sort
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The Select Operator 3
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The Plan?
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The Select Operator 4
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Delete Query
BEGIN TRAN
DELETE FROM Production.Product
WHERE ProductID = 3343
ROLLBACK TRAN
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The Plan
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Delete Operator
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Assert
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Table Spool
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A View
SELECT ve.FirstName,
ve.LastName,
ve.BusinessEntityID
FROM HumanResources.vEmployee AS ve
WHERE ve.BusinessEntityID = 221
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View Execution Plan
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The Real Plan
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A little XML
WITH XMLNAMESPACES(DEFAULT N'http://schemas.microsoft.com/sqlserver/2004/07/showplan'),
QueryPlans AS
(
SELECT RelOp.pln.value(N'@PhysicalOp', N'varchar(50)') AS OperatorName,
RelOp.pln.value(N'@NodeId',N'integer') AS NodeId,
RelOp.pln.value(N'@EstimateCPU', N'decimal(10,9)') AS CPUCost,
RelOp.pln.value(N'@EstimateIO', N'decimal(10,9)') AS IOCost,
dest.text
FROM sys.dm_exec_query_stats AS deqs
CROSS APPLY sys.dm_exec_sql_text(deqs.sql_handle) AS dest
CROSS APPLY sys.dm_exec_query_plan(deqs.plan_handle) AS deqp
CROSS APPLY deqp.query_plan.nodes(N'//RelOp') RelOp (pln)
)
SELECT qp.OperatorName,
qp.NodeId,
qp.CPUCost,
qp.IOCost,
qp.CPUCost + qp.IOCost AS EstimatedCost
FROM QueryPlans AS qp
WHERE qp.text LIKE 'SELECT * FROM HumanResources.vEmployee AS ve'
ORDER BY EstimatedCost DESC
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What To Look For
First Operator
Warnings
Most Costly Operations
Fat Pipes
Extra Operations
Scans
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Resources
Scarydba.com/Resources
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Grant Fritchey | www.ScaryDBA.com
Grant Fritchey
Product Evangelist for Red Gate Software
Twitter: @gfritchey
Blog: scarydba.com
Email: grant@scarydba.com
Grant Fritchey | www.ScaryDBA.com
Questions?
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