A Function by Any Other Name is a Function

Performance Impacts of User Defined Functions

Introduction

Jason Strate

e: [email protected]

e: [email protected]

b: www.jasonstrate.com

t: StrateSQL

Resources jasonstrate.com/go/Waits

MAKING BUSINESS INTELLIGENT www.pragmaticworks.com

Functions

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What Functions?

• User Defined Functions

– Scalar

– Inline

• Aka Table-Valued

– Multi-statement

• Aka Table-Valued

http://www.flickr.com/photos/mshades/3154733910/

CLR Functions Out of Scope

To use functions or not to use functions, that’s today’s

question.

Goals

1. Identify purposes for creating User-Defined Functions

2. Discuss the types of User-Defined Functions

3. Demonstrate performance impact in selecting different types of functions

Session Warranty

• Not a deep dive

– Inform those that don’t know

– Arm those that do know

• Not included

– Secret sauce

– Pixie dust

– Bacon

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A Function is a Function

• Benefits

– Consolidation

– Modularization

– Maintenance

– Reuse

• Performance

– Looking at impact versus gain

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Functions

Scalar

Inline Multi-statement

Scalar Functions

Parameter(s) Body

Statement(s) Value

Scalar Functions

• Function

– Single or multiple statement(s)

– Returns single value

• Usage

– SELECT, WHERE, ORDER BY

– CHECK Constraints

– Computed columns

Scalar Functions

• Cursor like behavior

– Linear performance effect

• Data Access

• Executes on

– SELECT

– WHERE

– ORDER BY

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Scalar Demo

Demo 001 – Scalar Functions

Scalar Performance

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Native Scalar

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Native Scalar

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Scalar Performance

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Functions

Scalar


Inline Functions

Parameter(s) Body -

Statement Table

Inline Functions

• Returns table parameter

– Columns defined in RETURN statement

• Parameterized View

• DML Operations allowed

– INSERT

– UPDATE

– DELETE

• Query-able results

Inline Functions

• Limitations

– Simple operations

– Duplication of access

Joining Functions

• APPLY

– CROSS = INNER

– OUTER = LEFT OUTER

• Pass in columns as parameters

– Replaces ON clause

Inline Demo

Demo 002 – Inline Functions

Inline Performance

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Functions

Scalar


Multi-Statement Performance

Parameter(s) Function Table

Didn’t we already see

this?!?


• Returns table parameter

– Columns defined in DDL

• Flexibility of Scalar function

• Flexibility of Inline function

• Query-able results

Multi-Statement Demo

Demo 003 – Multi-Statement Functions


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Summary

• Performance is important

– Other factors can be just as important

• Know the limitations

• Functions have a place

Resources

• http://msdn.microsoft.com/en-us/library/ms189294.aspx

• http://www.sqlteam.com/article/intro-to-user-defined-functions-updated

• http://www.amazon.com/Transact-SQL-User-Defined-Functions/dp/1556220790/ref=sr_1_1?ie=UTF8&s=books&qid=1268026139&sr=8-1

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For more information…

Name: Jason Strate Email: [email protected] Blog: www.jasonstrate.com Resource: jasonstrate.com/go/functions

A Function by Any Other Name is a Function

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