This is the deck I used as JSSUG event on 26th Aug

1. Microsoft SQL Server
Index Tuning
Kenichiro Nakamura

2. 16 MCPs for SQL
70-765 70-764 70-762
70-761 70-473 70-463
70-465 70-464 70-462
70-451 70-433 70-442
70-441 70-447 70-229
70-228
BI….???
Best tuning
5 mins query -> 0.02 sec.

3. What you will learn today
All about index (Mainly for read)
No auto tuning features
No ColumnStore Index
No DMV nor DMF
How to think about everything from index point
of views.

4. Take away
What is index and how to use it to tune SQL.

5. Goal
Let you feel you learn something
Demystify index turning myth
And confuse you all 

6. What is performance?
• Latency
• Throughput
• Best vs Optimized performance

7. What are bottlenecks?
CPU
RAM
Disk (HDD/SSD)
Network
Developer
Admin

8. What are bottlenecks
CPU – Speed, Cores (NUMA)
RAM – Speed, Size (NUMA)
Disk (HDD/SSD) – Speed Size
Network – Speed
Developer – Poor Query
Admin – Poor maintenance

9. How SQL stores data
IO matters

10. Question
Which cluster size is optimal for SQL Server?
• 4KB
• 8KB
• 16KB
• 32KB
• 64KB
• 128KB

11. Question
Fill factor should be:
• 0
• 50
• 70
• 100

12. Question
Which data can be stay together?
• Data, Log, TempDB all together
• Data, TempDB together
• Everything separate

13. Page
1 page = 8KB = 8192 byte
Header = 96 bytes
• Page ID
• Next Page Pointer
• Space
• Row #
Data = 8060 bytes
https://msdn.microsoft.com/en-US/library/ms143432(SQL.120).aspx

14. Extend
1 Extend = 8 Pages = 64KB
Mixed extent
Uniform extend
https://docs.microsoft.com/en-us/sql/relational-databases/pages-and-extents-architecture-guide?view=sql-server-2017

15. Fill factor
Avoid Page split but why?
May place pages into different extent => More IO
Split happens when data is inserted in the middle
Log?
Sequential Guid?

16. Compression
CPU usage vs IO
Backup
Columnstore
Pages
When to compress data?

17. Partitioning and Stretch database
Want to reduce IO
Partitioning
Avoid query unnecessary partitions
Move old data to other table
Stretch
Remove data from local by move old data to Azure
Archive??
Cannot query

18. Index basic
What’s index?

19. Question
How many clustered index a table can have?
• 1
• More than 1

20. Question
When adding clustered index, SQL creates index data in addition to the
table.
• True
• False

21. Question
Covering index is faster than non-clustered index
• Of course!
• No way!
• It depends……

22. Heap
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms188270(v%3dsql.105)
Keep inserting data

23. Clustered Index
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177443(v%3dsql.105)
Ordered by “Key(s)”
Clustered index is table
B-Tree structure

24. Nonclustered Index
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177484(v%3dsql.105)
Ordered by “Key(s)”
B-Tree structure
Leaf points to the table

25. Covering Index
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177484(v%3dsql.105)
Add additional column data to
index or leaf node.

26. Unique Index
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177484(v%3dsql.105)
Only unique value can be
stored in the index
Constraint vs Performance

27. Filtered Index
https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177484(v%3dsql.105)
Index for particular values

28. Execution Query Plan
Calculate cost

29. Question
Which elements will affect creating query execution plan?
• Statistics
• MDOP
• Memory Settings
• Cost threshold for parallelism
• Everything

30. Question
Clustered Index Scan is faster than Table Scan.
• True
• False

31. Question
If Clustered Index Scan cost is more than 90%, you should tune for
performance.
• True
• False

32. Show Query Plan
Include Estimated or Actual Execution Plan

33. Execution Query Plan
Arrow thickness presents data amount.

34. Table Scan and Clustered Index Scan
https://docs.microsoft.com/en-us/sql/relational-databases/showplan-logical-and-physical-operators-reference?view=sql-
server-2017
The Table Scan operator retrieves all rows from the table
specified in the Argument column of the query execution
plan. Table Scan is a logical and physical operator.
The Clustered Index Scan operator scans the clustered index
specified in the Argument column of the query execution plan.
Clustered Index Scan is a logical and physical operator.

35. Index Seek
https://docs.microsoft.com/en-us/sql/relational-databases/showplan-logical-and-physical-operators-reference?view=sql-
server-2017
The Clustered Index Seek operator uses the seeking ability of
indexes to retrieve rows from a clustered index. Clustered
Index Seek is a logical and physical operator.
The Index Seek operator uses the seeking ability of indexes to
retrieve rows from a nonclustered index. Index Seek is a
logical and physical operator.

36. Key Lookup
https://docs.microsoft.com/en-us/sql/relational-databases/showplan-logical-and-physical-operators-reference?view=sql-
server-2017
The Key Lookup operator is a bookmark lookup on a table with
a clustered index. The Argument column contains the name of
the clustered index and the clustering key used to look up the
row in the clustered index.
The use of a Key Lookup operator in a query plan indicates
that the query might benefit from performance tuning. For
example, query performance might be improved by adding a
covering index.

37. Sort
https://docs.microsoft.com/en-us/sql/relational-databases/showplan-logical-and-physical-operators-reference?view=sql-
server-2017
The Sort operator sorts all incoming rows.
The Argument column contains either a DISTINCT ORDER BY:()
predicate if duplicates are removed by this operation, or an
ORDER BY:() predicate with a comma-separated list of the
columns being sorted. Sort is a logical and physical operator.

38. Plan Cache
Arrow thickness presents data amount.

39. Best Practices
https://docs.microsoft.com/en-us/azure/virtual-
machines/windows/sql/virtual-machines-windows-sql-performance

40. Fin.