1. DISCOVERING
THE PLAN CACHE Jason Strate
Database Architect
Pragmatic Works, Inc.
SQL SATURDAY 211
CHICAGO

2. SESSION AGENDA
Session Goals
Viewing The Plan Cache
Showplan XML Structure
Scenarios and Demos
Wrap Up

3. SESSION GOALS
Viewing Showplan Scenarios
Session
The Plan XML and Wrap Up
Goals
Cache Structure Demos

4. SESSION GOALS
1. Discuss the plan cache
2. Explore the plan cache
3. Demonstrate methods
to query plan cache
4. Demonstrate
performance tuning
concepts

5. CONTENT COMPATIBILIT Y
SQL Server
2012
SQL Server
2008 (R2)
SQL Server
2005

6. VIEWING THE PLAN
CACHE
Viewing Showplan Scenarios
Session
The Plan XML and Wrap Up
Goals
Cache Structure Demos

7. PLAN CACHE
Portion of SQL Server memory that stores execution plans
that have been prepared by the Query Optimizer. Execution
plans are used to by SQL Server to execute SQL statements.

8. PLAN CACHE
Portion of SQL Server memory that stores execution plans
that have been prepared by the Query Optimizer. Execution
plans are used to by SQL Server to execute SQL statements.
Pros Cons
No setup Reset with service
Query-able Activity flush
Actionable Plans miss cache
Real World In Use

9. PLAN CACHE
 sys.dm_exec_cached_plans
• All Plans
• Size
• Use count
 sys.dm_exec_query_plan
(plan_handle)
• Table Valued Function
• SHOWPLAN XML as XML
 sys.dm_exec_text_query_plan
(plan_handle,0,-1)
• Table Valued Function
• SHOWPLAN XML as text

10. PLAN HANDLE
0x06000F001CF36A2640C1318A…
Varbinary(64)
Hash value
Identifies plan

11. WHERE IN THE WORLD IS PLAN_HANDLE?
sys.dm_exec_requests
 Current connection
 Vaguely similar to sp_who
sys.dm_exec_query_stats
 Stats on executed queries
 Contains SQL_Handle
sys.dm_exec_cached_plans
 Stats on cached plans
 Distinct list of plans
http://www.flickr.com/photos/fallentomato/3918329246/

12. SHOWPLAN XML
STRUCTURE
Viewing Showplan Scenarios
Session
The Plan XML and Wrap Up
Goals
Cache Structure Demos

13. GETTING STARTED
DBA-409-S

14. GETTING STARTED
DBA-409-S

15. GETTING STARTED
DBA-409-S

16. GETTING STARTED
DBA-409-S

17. EXECUTION PLAN
DBA-409-S

18. SHOWPLAN XML STRUCTURE
DBA-409-S

19. SHOWPLAN XML STRUCTURE
What is in it?
ShowPlanXML
BatchSequence
Batch
Statements
StmtSimple
http://www.flickr.com/photos/etringita/854298772/

20. GOING BELOW STMTSIMPLE
Missing Parameter Warnings RelOp
Indexes List •Plan Affecting •EstimateRows,
•Indexes that •Parameters Convert EstimateIO,
would improve passed into •Columns with PhysicalOp,
plan query no Statistics •Hash,
performance •Unmatched IndexScan,
Indexes NestedLoops
•OutputList

21. CAUTION
Volatile Cache
Data In Use
Use Be
Xquery Mindful

22. XQUERY FUNCTIONS
• Forward slashes
 / means to find the specific location
 // means find any from the current location
• Important Functions
• nodes()
• value()
• exist()
• query()
• Everything is case sensitive

23. SCENARIOS AND DEMOS
Viewing Showplan Scenarios
Session
The Plan XML and Wrap Up
Goals
Cache Structure Demos

24. MISSING INDEXES
What plans would benefit from indexes?
 DMVs
 sys.dm_db_missing_index_columns
 sys.dm_db_missing_index_details
 sys.dm_db_missing_index_group_stats
 sys.dm_db_missing_index_groups
DBA-409-S

25. MISSING INDEXES
What plans would benefit from indexes?
 DMVs
 sys.dm_db_missing_index_columns
 sys.dm_db_missing_index_details
 sys.dm_db_missing_index_group_stats
 sys.dm_db_missing_index_groups
What Queries
Should I Test?
http://www.flickr.com/photos/fallentomato/3918329246/

26. MISSING INDEXES Demo 1

27. CONVERSION WARNINGS
Data types matter? Here lies your
 varchar vs. nvarchar transaction
 scan vs. seek
What plans have this issue?

28. OTHER WARNINGS
Columns Unmatched Spill to
with no Indexes Tempdb*
Statistics

29. IMPLICIT CONVERSIONS Demo 2
AND OTHER WARNINGS

30. POOR PARAMETER SNIFFING
Think about the plans you
find example…
 What has changed in the
environments?
 Is the plan using the wrong
values?
What parameters is the
plan using?

31. PARAMETER Demo 3
SNIFFING

32. STATEMENT INFORMATION
What’s the parallelism trigger?
• Parallelism is cost based
• Query cost default 5

33. QUERY TREE ESTIMATES
What does SQL Server expect?
• CPU
• IO
• Rows
• Cost

34. QUERY PROPERTIES Demo 3

35. LET’S GET PHYSICAL

36. PHYSICAL OPERATIONS Demo 5

37. INDEX OPERATIONS
 Access Methods:Full Scans/sec

38. INDEX OPERATIONS
 Access Methods:Full Scans/sec

39. INDEX OPERATIONS
What about large tables?
 Scans?
 Good?
 Bad?
What do you do when you
see large counts of scans
on an index?

40. INDEX OPERATIONS
What plans are using that index?
 Should you drop it?
 What is the potential effect?
http://www.flickr.com/photos/s3a/4436302537/

41. INDEX OPERATIONS Demo 5

42. KEY LOOKUP
Find value in one index
Look up more columns in clustered index

43. DEEPER FOR INCLUDED INDEXES
You found them…
NOW fix them…
The information is in the plan!
• Investigate the nodes
• Pull in the data!

44. KEY LOOKUPS & Demo 4
INCLUDED COLUMNS

45. WRAP UP
Viewing Showplan Scenarios
Session
The Plan XML and Wrap Up
Goals
Cache Structure Demos

46. FIND YOUR OWN TREASURE
 http://schemas.microsoft.com/sqlserver
 /2004/07/showplan/showplanxml.xsd

47. SUMMARY
1. Plan Cache IS your
performance work load
2. Information is readily
available
3. Techniques to access
not as complex as
appearances
4. Scale your performance
knowledge across the
environment

48. SQL SERVER MVP DEEP DIVES, VOLUME 2
 www.operationsmile.org
 www.manning.com/delaney

49. RESOURCES
Jason e: jstrate@pragmaticworks.com
Strate
e: jasonstrate@gmail.com
b: www.jasonstrate.com
t: StrateSQL
Resources jasonstrate.com/go/Cache2013