1. SQL Server Query and Index Tuning
Mladen Prajdić
dSolutions SI

2. About me

3. Server troubleshooting Data structures
Agenda
Server troubleshooting
Data structures
Indexing practices and troubleshooting
Query tuning

4. Server troubleshootinG
Perfmon
SQL Profiler, SQL Trace
Event Notifications
Extended Events
DMVs
sys.dm_os_wait_stats
sys.dm_exec_requests
sys.dm_exec_sql_text
sys.dm_exec_query_plan
sys.dm_tran_locks

5. Server troubleshooting Data structures
Agenda
Server troubleshooting
Data structures
Indexing practices and troubleshooting
Query tuning

6. Data Pages in no logical order No page deallocations with delete
Data structures HEAP
Bulk inserts
Staging tables
Data Pages in no logical order
No page deallocations with delete

7. Data structures clustered index
Data pages are logically ordered
All data on the leaf node
Fill factor
Uniquifier

8. Data structures Nonclustered index
Pointers to actual pages with data
CI key or RID
Uniquifier
Included columns

9. Server troubleshooting Data structures
Agenda
Server troubleshooting
Data structures
Indexing practices and troubleshooting
Query tuning

10. Indexing practices and troubleshooting
THE ENDLESS CLUSTERED INDEX DEBATE
Clustered index <> Primary Key
Int, DateTime, Guid, Composite columns
Page splits
Fragmentation (CI and NCI)

11. Indexing practices and troubleshooting
THE ENDLESS CLUSTERED INDEX DEBATE
Type
CI width (b)
Rows
NCI num
Size(Mb)
INT 4 10
57.2
DATETIME 8
114.5
GUID 16
228.9
OTHER 32
457.8
Know your data!

12. Indexing practices and troubleshooting
Problem?
Diagnose
Tune
Test
INDEX
ANALYSIS

13. Indexing practices and troubleshooting
MISSING INDEXES
3 DMVs, Database Tuning Advisor, SSMS suggestions
UNUSED INDEXES
sys.dm_db_index_usage_stats
FRAGMENTED INDEXES
sys.dm_db_index_physical_stats

14. Indexing practices and troubleshooting
INDEXING POINTERS
Foreign keys
One multicolumn or multiple single column indexes
Beware of Bookmark Lookup
Included columns

15. Indexing practices and troubleshooting
TIPPING POINT
Only valid for non-covering nonclustered indexes

16. Indexing practices and troubleshooting
ENTERPRISE EDITION FEATURES
Compresion
sp_estimate_data_compression_savings
Filtered indexes
Somewhat limited functionality

17. Indexing practices and troubleshooting
STATISTICS
Value frequency histogram
Async auto update stats
Needed to build better execution plans
Multicolumn, Custom and Filtered stats

18. Indexing practices and troubleshooting
STATISTICS

19. Indexing practices and troubleshooting
QUICK SUMMARY
Narrow, increasing values for keys
Try to eliminate bookmark lookup
Included columns are your friend
Statistics maintenance

20. Server troubleshooting Data structures
Agenda
Server troubleshooting
Data structures
Indexing practices and troubleshooting
Query tuning

21. SQL Profiler, SQL Trace, Extended events SET STATISTICS IO
Query tuning
SQL Profiler, SQL Trace, Extended events
SET STATISTICS IO
SET STATISTICS TIME
Execution Plans
Minimize logical reads and CPU

22. Solution for every performance problem
Query tuning
Solution for every performance problem
NOLOCK
JUST KIDDING 

23. Report query with UDF and correlated subqueries in the select list
Query TunNing
Example:
Report query with UDF and correlated subqueries in the select list
We‘ll make it GO FASTER! 

24. Forced Parameterization
„Magic“ bullets
Forced Parameterization
Optimize for ad hoc workloads

25. Don‘t just add or remove indexes blindly Think set based
Summary
Know your data
Don‘t just add or remove indexes blindly
Think set based
Scalar UDFs bad, Table valued UDFs good
Use CROSS APPLY

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