5 ways to improve performance through indexing

5 Ways to Improve Performance
through Indexing

Jason
Strate
e: jstrate@pragmaticworks.com
e: jasonstrate@gmail.com
b: www.jasonstrate.com
t: StrateSQL
Resources jasonstrate.com/go/indexing
Introduction
MAKING BUSINESS INTELLIGENT
www.pragmaticworks.com

• Founded 2008 by MSFT MVP Brian Knight
• Focused on the MSFT SQL Server Platform
• Provides services, training and software
• MSFT/HP “go to” partner:
• Gold Certified:
o BI
o Data Management
o SQL Performance
• Team led by multiple MVP’s
• Offices throughout the US with Corporate
HQ in Jacksonville, FL
Pragmatic Works Company History

5 Ways to Improve
Performance through
Indexing

Lookup Imbalance
• Excessive key lookups
– Exceed number of seeks
• Problems
– Increased CPU
– Increased IO
– Increased duration

Possible Solutions
• Ignore the problem
– Choose high key lookup rate
• Move clustered index
– Maybe the key is wrong
• Add included columns
– Improve NC indexes

Case Study 1
• What’s wrong?
• Do you see the pattern?
• What do you do?
– Move clustered index

Case Study 2
• What’s wrong?
• What do you do?
– Move clustered index
– Add included columns

Case Study 3
• What’s wrong?
• What do you do?
– Add included columns

November 6-9, Seattle, WA
Lookup Imbalance
• Demo

Lookup Imbalance Summary
• Key lookups should not exceed seeks
• Investigate “WHY” when they do
• Consider whether to:
– Move the clustered index
– Add included columns to non-clustered indexes
• Usage patterns will shift over time

Scan Heavy Indexes
• High scans on large indexes
– Exceed seeks
• Problems
– Increased IO
– Increased locking
• Potential deadlocks
– Affect page life expectancy
– Impact memory distribution

Case Study 1
• Metric is high, so what?
• How do you tie into performance counter?
– Sys.dm_db_index_usage_stats
– Plan cache
Access Methods:Full Scans/sec

Case Study 2
• What’s wrong?
• Why aren’t the other indexes used?
• Are the right indexes in place?
• What do you do?
– Examine execution plans
– Add in correct indexes

Scan Heavy Indexes
• Demo

Scan Heavy Indexes Summary
• High scans on indexes can impact performance
– Higher IO
– More locking
• More Blocking
• Possible Deadlocking
– Memory impacted
• Find the occurrences
– Identify indexes and analyze plans
– Add alternative indexes

Filtered Indexes
• Index with a WHERE clause
– Only includes filtered rows
– Decreases rows in index
• Effect
– Improved plan quality
– Improved storage
– Lower build time
– Less maintenance
• Benefit
– Scan of small set of data

Case Study
• New data coming this week
– Represents < 1% of rows
• Can’t rebuild indexes
– Statistics on new rows inaccurate
• Need high quality plans
– Indexes in place aren’t used
• What do you do?

Filtered Index Issue
• Filter Criteria
– Must be included
– Can not be parameterized
• Plan warning
– Unmatched indexes

Filtered Indexes
• Demo

Filtered Index Summary
• Consider filtered indexes for:
– Large indexes with limited range of use
– Tables with large number of new rows
• Improves index performance
– Smaller, lightweight, agile
– Improved plan quality
• Seeks over scans (small data over large data)
• Scans over seeks (tiny data over small data)

Missing Indexes
• Optimize through materialization
– Index versus statistics
• Three options
– Dynamic management views
– Database Engine Tuning
Advisor
– Plan Cache

Missing Indexes
MISSING
INDEXES!!!

Missing Indexes
• Demo

Missing Index Summary
• These are FREE recommendations
– Results of actual performance opportunities
– Provide opportunity to focus on other needs
• These are recommendations
– Index schema to ensure value
– Consolidate when possible
– Review associated queries

Indexing Foreign Keys
• Foreign keys enforcement
– INSERT
– UPDATE
– DELETE
• Performed in background
• Unseen until a problem

Indexing Foreign Key Issues
• Unindexed foreign key
– Constraint columns
• Performance issues
– Scan of column values
– Increased locking
– Blocking likely
– Potential deadlocking

Case Study
Delete from SalesOrderHeader?

Case Study
Delete from SalesOrderDetail?

Case Study
Delete from SalesOrderHeaderSaleReason?

Indexing Foreign Keys
• Demo

Indexing Foreign Key Summary
• Foreign keys are important
– Enforce integrity of data
– Constraints on values
• Operations occur in background
– DELETEs often source of issues
– Can lead to deadlocks

Learn More About Indexes

Services
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rapid development services from
Pragmatic Works.
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platform and simplify development on
the platform.
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means to get into information technology
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For more information…
Name: Jason Strate
Email: jstrate@pragmaticworks.com
Blog: www.jasonstrate.com
Resource: jasonstrate.com/go/indexing

5 ways to improve performance through indexing

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