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3 query tuning techniques every sql server programmer should know
This document discusses various query tuning techniques that SQL Server programmers should know. It covers understanding how queries work and set theory, testing queries, formatting T-SQL for readability, using appropriate predicates and set theory operations, avoiding implicit conversions, and using locks appropriately. The document also includes diagrams of the SQL Server architecture and physical query tree to illustrate how queries are processed.
3 query tuning techniques every sql server programmer should know
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- 2. Query Tuning TechniquesEvery SQL Server Programmer Should Know Rodrigo Crespi
- 3. Rodrigo Crespi MCSE, MCSA,etc. PostDegree in Data Base – UGF PASS Chapter Leader – SQL Server RS University Professor of Database Management CrespiDB | Soluções em Plataforma de Dados @SQLCrespi rodrigocrespi S Q L C r e s p i sqlcrespi.com SQLCrespi
- 4. First of All! ●Understand how a query works; ● Understand set theory; ● Most important try another thought.
- 5. SQL Server Architecture P r o t o c o l o s Parser Optimizer SQLMgr. DB. Mgr. Query Executor R e l a t i o n a l E n g i n e S t o r a g e E n g i n e T-Services Lock Mgr. File Mgr. Utilities Access Methods SQLOS SQLOS.dll SQLLang.dll PageLock Monitor Resource Monitor Lazy Writer Scheduler Monitor SQLmin.dll Buffer Pool Memory Mgr. Scheduling Sinc. Services Lock Mgr. I/O SQLDK.dll It’s a simple representation
- 6. Relational Engine Optimizer Query Executor Cmd Parser SNI ProtocolLayer Storage Engine Transactio n Manager Access Methods Buffer Manager Lock Manager Data Cache Plan Cache Data File T-SQL Select * from cliente T D S IF Query Tree O L E D B IF Buffer Pool Query Workspace Query Compile Token Perm XEvents,Metadados, outros...
- 7. Relational Engine Optimizer Query Executor Cmd Parser SNI ProtocolLayer Storage Engine Transactio n Manager Access Methods Buffer Manager Data File T-SQL Update cliente set nome = ‘Rodrigo’ T D S IF Query Tree O L E D B IF Lazy Writer CheckPoint Lock Manager Data Cache Plan Cache Buffer Pool Query Workspace Query Compile Token Perm Xevents,Metadados, outros... Dirty Page
- 8. Physical Query Tree •It is the way the optimizer calculates the most efficient path for executing the command; • More efficient or more optimized?
- 9. Zoom of Optimizer Parsing/ binding Simplification Start a joins set Trivial Plan Optimization phase Search 0 Search 1 Search 2 Phase 0-Traditional: nested Loops, with no parallelism options. Phase 1 – Fast: Uses a fast subset of rules that contains the most common patterns. Phase 2 – Complete: For complex queries with parallelism and indexed views. Before Optimization Optimization
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- 11. The best pattern isthe one that every team follows! Pattern
- 12. Formatting T-SQL forReadability ● Comments, author, and brief audit trail; ● Be Consistent; ● The best formatting pattern is the one that is followed by the entire team.
- 13. How To Testa Query ● Clear caches; ● Try, Test and Compare; ● Set measurements; ● DMVs for check; ● Clone Database.
- 14. T-SQL Performance • SetStatistics IO / Time; • Compare the execution plans;
- 15. Predicates and SetTheory ● Say no to cursor; ● The Optimizer can’t pick the best execution plan if the Stored Procedure is broken up into many parts; ● Built-In functions that can affect performance; ● Like; ● And | Or | In; ● Union and union all; ● IsNull();
- 16. Implicit Conversions ● Theoptimizer chooses the data type based on a predefined list; ○ https://docs.microsoft.com/en-us/sql/t-sql/data-types/data- type-precedence-transact- sql?redirectedfrom=MSDN&view=sql-server-ver15 ● Data Types matter; ● You may not get what you expect; ● Implicit conversions can be costly.
- 17. Lock and NoLock Lockis required in SQL Databases. This is a true! HOWEVER, if you use hint nolock pay attention if you reading a dirty page!
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