The Plan Cache Whisperer - Performance Tuning SQL Server
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Execution plans tell SQL Server how to execute queries. If you listen closely, execution plans can also tell you when performance-tuning opportunities exist in your environment. By listening to your queries, you can understand how SQL Server is operating and gain insight into how your environment is functioning. In this session, learn how to use XQuery to browse and search the plan cache, enabling you to find potential performance issues and opportunities to tune your queries. In addition, learn how a performance issue on a single execution plan can be used to find similar issues on other execution plans, enabling you to scale up your performance tuning effectiveness. You can use this information to help reduce issues related to parallelism, shift queries from using scans to using seek operations, or discover exactly which queries are using which indexes. All this and more is readily available through the plan cache.
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The Plan Cache Whisperer - Performance Tuning SQL Server
- 1. The Plan Cache Whisperer Performance Tuning SQL Server Jason Strate, Principal Consultant, Pragmatic Works
- 3. Without knowledge action is useless and knowledge without action is futile. - Abu Baker
- 6. Scale Up Your Skills 6
- 7. 7 What types of execution plan performance issues do you watch for?
- 8. 8 What do you think about this?
- 9. Agenda Plan Cache Foundation Relational Operators Index Analysis Execution Patterns
- 10. Plan Cache Foundation Plan Cache Foundation Relational Operators Index Analysis Execution Patterns
- 11. What is the plan cache? • SQL Server memory • Stores execution plans • From Query Optimizer • Used to execute SQL statements.
- 12. Plan Cache sys.dm_exec_cached_plans • All Plans • Size • Use count sys.dm_exec_query_plan • Table Valued Function • SHOWPLAN XML as XML sys.dm_exec_text_query_plan • Table Valued Function • SHOWPLAN XML as text
- 13. 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
- 14. Getting Started
- 15. Execution Plan
- 17. Demo Plan Cache DMVs and SHOWPLAN XML
- 18. Relational Operators Plan Cache Foundation Relational Operators Index Analysis Execution Patterns
- 19. Relational Operators Activities within execution plan • Clustered Index Scan • Merge Join • Compute Scalar • Filter Describe the operation Both logical and physical
- 22. What do I need? Where am I using it? Quality vs. Quantity? Indexing Problems
- 23. Missing index 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 do you test? What do I need? http://www.flickr.com/photos/fallentomato/3918329246/
- 24. Increasing index scans? How do you correlate perf stats? • Access Methods:Full Scans/sec Dynamic management view • sys.dm_db_index_usage_stats • sys.dm_db_index_operational_stats Where am I using it?
- 25. What plans are using an index? • What is the potential effect? • Does it impact any critical processes? • Should you drop it? Quality vs. Quantity? 25
- 28. Are Key Lookups Bad? SELECT SalesOrderID, SalesOrderNumber, OrderDate, DueDate, ShipDate FROM Sales.SalesOrderHeader WHERE CustomerID = 11238
- 29. Functions and Predicates SELECT * FROM Sales.SalesOrderHeader soh INNER JOIN Sales.SalesOrderDetail sod ON sod.SalesOrderID = soh.SalesOrderID WHERE dbo.CleanSalesOrder(sod.SalesOrderID) < 43665 29
- 31. Your Call To Action Be creative in using your performance tuning knowledge Think of performance issues as patterns Always prioritize your performance tuning efforts
- 32. 32 Explore Everything PASS Has to Offer FREE ONLINE WEBINAR EVENTS FREE 1-DAY LOCAL TRAINING EVENTS LOCAL USER GROUPS AROUND THE WORLD ONLINE SPECIAL INTEREST USER GROUPS BUSINESS ANALYTICS TRAINING VOLUNTEERING OPPORTUNITIES PASS COMMUNITY NEWSLETTER BA INSIGHTS NEWSLETTERFREE ONLINE RESOURCES
- 33. 33 Session Evaluations ways to access Go to passSummit.com Download the GuideBook App and search: PASS Summit 2015 Follow the QR code link displayed on session signage throughout the conference venue and in the program guide Submit by 5pm Friday November 6th to WIN prizes Your feedback is important and valuable.
- 34. Thank You Jason Strate e: jstrate@pragmaticworks.com e: jasonstrate@gmail.com b: www.jasonstrate.com t: StrateSQL
Editor's Notes
- http://www.cx.com.s3.amazonaws.com/img/wp/blog/slow-website.jpg When I first started talking to people about querying the plan cache, it was about interesting things. But the more I’ve gotten into looking at the plan cache, I’ve found that the value is find slowly performing items and finding new ways to make that problem actionable.
- https://s3-us-west-1.amazonaws.com/kout.io/whatyoudotoday_2880x1800.jpg What I want to discuss today is how you take something you know and expand that to a more holistic view of your entire platform.
- http://www.fastcompany.com/3037224/fast-feed/whispers-no-good-very-bad-day So we’re going to look at how we can start talking differently to our SQL Server to better understand the problems it is encountering and how you can take different actions.
- Some plans (bulk insert, no recompile) don’t exist in cache after execution Pros No setup Query-able Actionable Real World Cons Reset with service Activity flush Plans miss cache In Use
- Varbinary(64) Hash value Identifies a plan
- What indexes do I need? Where am I using indexes?