1. Reading execution plans successfully
Arthur Daniels
Reading execution plans successfully

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October 30th Through November 3rd
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5. DBA-Art.com Twitter: @ArthurDanSQL
Presentation slides + demos Step-by-step instructions for setting up a test server at home:

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Intro
3 years working with SQL Server Presented at SQL Sat Iowa City “I don’t care how long my query takes as long as it returns results”

7. Overview What makes up an execution plan?
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Overview
What makes up an execution plan?
What do the operators inside the execution plan mean?
What you can infer from your plan

8. My test environment SQL Server 2014 - Developer AdventureWorks 2014
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My test environment
SQL Server Developer AdventureWorks 2014

9. Your environment matters
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Your environment matters
Hardware
SQL Settings
Min Max Memory, Cost Threshold for Parallelism
SQL version

10. Graphical Execution Plan
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Graphical Execution Plan
What’s that?

11. Other execution plan features
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Other execution plan features
Flow and size of line

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Where and what are they?
Graphical Execution Plans are stored as XML SQL Server Management Studio (SSMS) SQL Server Plan Cache Live Query Stats Query Store?

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The Plan Cache
sys.dm_exec_cached_plans (2008) Plan cache contains estimates Emptied when server restarts

14. Plan cache demo To-do: Build plan cache Find our specific plan
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Plan cache demo
To-do:
Build plan cache
Find our specific plan
Look at operator
View actual plan’s rows vs estimated.

15. Graphical Execution Plan
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Graphical Execution Plan
Plan Operators
Index Seek Index Scan Key Lookup

16. Where do the estimates come from?
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Where do the estimates come from?
SQL Server automatically generates statistics
One statistic per index
One statistic per column once a query searches by that column
Search as in Where clause, JOINs

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Statistics Demo
Open Statistics on IX_TransactionHistoryArchive_ProductID

18. Statistics General Used for execution plan estimates
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Statistics General
Used for execution plan estimates
Automatically generated
One for each index
One for each column*
Statistics contain header, density vector and histogram

19. Reading deeper Parallelism as operators
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Reading deeper
Parallelism as operators
Gather Streams Distribute Streams Repartition Streams

20. Comparing a parallel query to serial query
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Comparing a parallel query to serial query
Demo Set Cost Threshold for Parallelism to 1 for this demo

21. Compute Scalar Operator
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Compute Scalar Operator
Used for mathematical expressions Referred to as “Expr”

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Compute Scalar Demo
Demo here

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Implicit Conversion
Why? In actual and estimated

24. Reading Implicit Conversions
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Reading Implicit Conversions
Demo

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Missing Index Hints
Execution plan will contain index suggestions Only the first missing index is shown

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Missing Indexes
Demo

27. Tools inside SQL Server 2016
Query Store Live Query Statistics

28. Conclusions

29. Wrap-Up How SQL estimates cost Operators: Index Scan, Index Seek
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Wrap-Up
How SQL estimates cost
Operators:
Index Scan, Index Seek
Parallelism
Compute Scalar
Implicit Conversions
Missing Indexes

30. Finally, what you can infer
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Finally, what you can infer
Look at size of lines between operators Discover what operators are doing Search your plan cache for hidden problems

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Questions?
You can also contact me on or my website,

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Useful links
Finding Implicit Conversions in your Plan Cache Free graphical plan explorer: