Dave LinkedIn

 13 years DBA Experience  Teaching SQL Server since 1999  SQL Server Instructor at Harper College, Palatine, IL  Currently supervise a team of DBAs  DBA consultant for Einstein Technology Solutions, Lombard, IL

Certifications

 How does SQL Server execute a query  Types of Execution Plans  Common query bottlenecks  Plan Cache  First Look at an Execution Plan  Execution Plan Icons and Identifying potential performance bottlenecks  SQL Sentry Plan Explorer

“ An execution plan, simply put, is the result of the query optimizer's attempt to calculate the most efficient way to implement the request represented by the T-SQL” Grant Fritchey - SQL Server Execution Plans Second Edition

 Minimum permissions needed: ShowPlan in the database  Members of Sysadmin role  Members of DB_Owner

 Disk I\O  CPU  Memory  Network  Poor query design  Missing indexes  Indexes not optimized  Statistics out of date

 Types of Plans ◦ Actual ◦ Estimated  Displaying Execution Plans ◦ Graphical plans ◦ Text plans (deprecated) ◦ XML plans  Saving ◦.SQLPLAN

 Algebrizer process creates a hash of incoming query(DML Only)  What flushes a plan from Cache ◦ Not enough memory ◦ DBCC FREEPROCCACHE ◦ Schema Changes to referenced objects ◦ Statistics used by the plan are updated ◦ Changes made to the stored procedure

Used for comparative purposes Float cursor over icon

 Index Scan vs Index Seek Scan searches data pages Seek is preferred for highly selective queries If scan, check for index or a useful index

 Usually considered less than optimal  If table is very small may not be an issue  If expecting an Index Scan or Seek:  Update statistics  Rebuild indexes  Review query

 Can be difficult to test on a development machine  Some statements can force a serial plan

 Use of cursor with sys.sp_Msforeachdb  Data type conversions  Foreign Key full table scan due to lack of index

 Happens when joining on different data types  Can lead to excessive CPU utilization  Can occur in the FROM or the WHERE clause

In this case, this is the Estimated Execution plan, actual was more accurate

 Only retrieve what you need  Minimize use of temporary tables  Avoid cursors  Work with your DBA to arrange good indexes to support filters, joins and ordering  Learn how to address tasks with different query approaches to compare performance

 Must have a baseline for normal performance  Establish at different times of day  Document the baseline

 Table redesign  Redesign query  More memory  Add Indexes  Optimize indexes  Update statistics  Reboot

 Microsoft SQL Server 2014 Query Tuning and Optimization – Benjamin Nevarez      Paul White Blog Paul White Blog

 Understanding Parallelism Understanding Parallelism  BrentOzar.com BrentOzar.com  SQL Server Execution Plans – Grant Fritchey 

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