sql server - using tools to analyze query performance

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Using Tools to Analyze Query Performance

CHAPTER 14

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About the Author

Marek Maśko• Principal Database Analyst at Sabre

• Working with SQL Server since 2010

• SQL DBA, Dev & Architect

• MCP since 2012

• Contact Information: Email: marek.masko@gmail.com

LinkedIn: https://pl.linkedin.com/in/marekmasko

Twitter: @MarekMasko

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Agenda

• Query Optimizer

• SQL Trace

• SQL Server Profiler

• SQL Server Extended Events

• SET Session Options

• Dynamic Management Objects

• Execution Plans

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QUERY OPTIMIZER

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Query Performance

• Time

• CPU

• Memory

• I/O

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Query Optimization

Relational EngineT-SQL

Statement Parser AlgebrizerQuery

Optimizer

Storage Engine

Query Parsing

Parse Tree

Normalization and Binding

Query Processor

Tree

Query Optimization

Execution Plan

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Query Optimizer

• Cost based

• Cardinality Estimation

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SQL TRACE & SQL SERVER PROFILER

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SQL Trace & Profiler

https://msdn.microsoft.com/en-us/library/hh245121.aspx

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Benefits and drawbacks

• Easy to use

• Produces overhead:

– Local resources

–Network

• Results grid can consume a lot of memory

• Deprecated!

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SQL SERVER EXTENDED EVENTS

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Extended Events Engine

https://technet.microsoft.com/en-us/library/dd822788(v=sql.100).aspx

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Extended Events Engine

https://technet.microsoft.com/en-us/library/dd822788(v=sql.100).aspx

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SET SESSION OPTIONS

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SET Session Options

• SET STATISTICS IO

• SET STATISTICS TIME

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DYNAMIC MANAGEMENT OBJECTS

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DMO

• System views and functions

• More than 130

• Exist in sys system schema

• Names start with dm_

• Shows current state or data cumulated from instance start

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DMO

• SQLOS related

• Execution related

• Index related

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Most Important DMOs

• dm_exec_requests

• dm_exec_sessions

• dm_exec_sql_text()

• dm_exec_query_stats

• dm_os_wait_stats

• dm_os_waiting_tasks

• dm_db_missing_index_details

• dm_db_missing_index_columns

• dm_db_missing_index_groups

• dm_db_missing_index_group_stats

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EXECUTION PLANS

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Estimated and Actual Execution Plans

Estimated execution plan

• Output from the Optimizer

• Query doesn’t have to be executed

• Tells you what SQL Server would most likely do

• Stored in the plan cache

Actual execution plan

• Output from the actual query execution

• Tells you exactly what SQL Server did

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Execution Plan Formats

• Graphical Plans

• Text Plans

• XML Plans

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Graphical Plan

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Text Plan

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XML Plan

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SET Session Options

• Text plans

– SET SHOWPLAN_TEXT and SET SHOWPLAN_ALL for estimated plans

– SET STATISTICS PROFILE for actual plans

• XML plans

– SET SHOWPLAN_XML for estimated plans

– SET STATISTICS XML for actual plans

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THANK YOU!

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Resources

• Book: Training Kit Exam 70-461

• Scripts for Training Kit