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Advanced Index Tuning

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Brent Ozar• SQL Server MVP

for Quest Software• SQLServerPedia Ed.• SQL, SAN, VM admin• Dot-com-crash

experience• Performance freak• Twitter @BrentO• Blog: www.BrentOzar.com

Photo Source http://www.flickr.com/photos/vasta/415625308/

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Today’s Agenda• Passive Tuning• Active Tuning• Index Compression• The Silent Killer• Resources and Q&A

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Passive Tuning with DMVs

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DMV Tuning Lifecycle

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Removing Indexes

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Results

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Why Are Writes Different?

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Our Table: Items

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Indexes On An “Item” Table• Index #1:

– UPC_Code• Index #2:

– SupplierID• Index #3:

– Category– QtyInStock

Photo licensed with Creative Commons from:

http://www.flickr.com/photos/revolute/1944742197/

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Data In The Index

Category Qty in Stock Item ID

Bacon 45 1

Bacon 47 2

Bacon 98 3

Bacon 110 5

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But When It Changes…

Category Qty in Stock Item ID

Bacon 45 1

Bacon 42 2

Bacon 200 3

Bacon 110 5

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That’s Why…

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Our Query

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A Better Way: Includes

CREATE INDEX

IX_Category_Includes

ON dbo.Items (Category)

INCLUDE (QtyInStock)

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And When It Changes…

Category Qty in Stock Item ID

Bacon 45 1

Bacon 42 2

Bacon 200 3

Bacon 110 5

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Query Plan

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Remember, Never SELECT *

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Leave a Bread Crumb Trail

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DMV Tuning Lifecycle

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Missing Index Query

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Okay – Now What?

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When Do We Add Indexes?

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DMV Tuning Lifecycle

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Active Tuning: The Wizards

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Danger! Danger!

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The End Result

CREATE NONCLUSTERED INDEX

[_dta_index_Activity_11_1977058079__K1_K4_K7_K5_K3] ON [dbo].[Activity]

(

[ServerName] ASC,

[ActivityTypeID] ASC,

[StatusTypeID] ASC,

[StartTime] ASC,

[DatabaseID] ASC

)

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Rename Each Index

CREATE NONCLUSTERED INDEX

[IX_ServerName_ActivityTypeID_StatusTypeID_StartTime_DatabaseID] ON

[dbo].[Activity]

(

[ServerName] ASC,

[ActivityTypeID] ASC,

[StatusTypeID] ASC,

[StartTime] ASC,

[DatabaseID] ASC

) ON [PRIMARY]

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Makes Ongoing Tuning Easier

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Active Tuning Summary• Don’t just click apply• Use smart names• Look for overlaps• Go passive first

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SQL 2008 Data Compression

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Estimating Compression

sp_estimate_data_compression_savings– @schema_name– @object_name– @index_id– @partition_number– @data_compression

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Index Compression Drawbacks• Enterprise Edition only• No inheritance• No automation

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The Silent Performance Killer

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Pretend You’re SQL Server

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http://www.flickr.com/photos/quacktaculous/3143079032/

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13% to 460%

Faster

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Absolutely No:• App changes• Vendor issues• Testing required• Guessing on indexes• Backfires

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Not All Unicorns and Roses• Standard Edition: Offline Only• Enterprise Edition: Most Online• Generates a lot of transaction logs

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The Native Solution

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The Better Way: T-SQL Code

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Don’t Reinvent The Wheel

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http://www.brentozar.com/go/faster