SQL Server - Inside Optimizer Engine
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The document discusses topics covered in an SQL Server Optimizer seminar, including: - Optimizer limitations with filtered indexes and how redundant predicates may be needed. - Forcing parallel query execution plans and actions that force serial plans. - Statistics on ascending columns and how trace flags can address problems on large tables. The document provides conclusions and key points from demos on each topic. It outlines an agenda for the seminar with times for presentations, breaks, and questions.
SQL Server - Inside Optimizer Engine
- 1. Inside SQL Server Optimizer By Hamid Jabarpour Fard
- 2. Hamid Jabarpour Fard Consultant / Author / Trainer / Speaker Data Platform Specialist, Fard Solutions Sdn. Bhd. Email: Hamid@Fard-Solutions.com Website: http://www.Fard-Solutions.com
- 3. Agenda Optimizer Limitations with Filtered Indexes Forcing a Parallel Query Execution Plan Statistics on Ascending Columns Questions and Answers 15 Minutes Break
- 4. Optimizer Limitations with Filtered Indexes Demo
- 5. Optimizer Limitations with Filtered Indexes Conclusion Redundant join predicates can be necessary to match filtered indexes. Filtered unique indexes do not provide uniqueness information to the optimizer. In some cases it may be practical to simply add the redundant predicates to every query.
- 6. Forcing a Parallel Query Execution Plan Demo
- 7. Forcing a Parallel Query Execution Plan Conclusion Below actions make serial plan in SQL Server Table variable’s content modification. Any T-SQL scalar function. CLR scalar functions marked as performing data access. Random intrinsic functions including OBJECT_NAME, ENCRYPTBYCERT and IDENT_CURRENT. System table access. (e.g. sys.tables) TOP Sequence Project (e.g. ROW_NUMBER, RANK) Recursive CTEs
- 8. Forcing a Parallel Query Execution Plan (Cont.) Conclusion Even experts with decades of SQL Server experience and detailed internal knowledge will want to be careful with trace 8649 flag.
- 9. Statistics on Ascending Columns Demo
- 10. Statistics on Ascending Columns Conclusion This is just an alternative way to fix a problem that is seen with large tables with ascending columns. The best solution is to update statistics periodically. Trace flag 2389 will work only for columns branded as ascending. Trace flag 2390 does not make sense to do so because it will stop working when the column turns out to be ascending.
- 12. Thanks For Attending This Event.