Performance Tuning for Visualforce

and Apex

Stuart Bernstein

ISV Technical Evangelist

Thomas Harris

LMTS, CCE Production Support

John Tan

SMTS, CCE Technical Enablement

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Stuart Bernstein

ISV Technical Evangelist

Thomas Harris

LMTS, CCE Production Support

John Tan

SMTS, CCE Technical Enablement

Introduction

This session is designed to help with common Visualforce/Apex

performance issues targeted towards intermediate/advanced

Force.com developers.

Agenda

SOQL/SOSL

Batch Apex

Record Lock Contention

Visualforce

Debugging Tools

Q & A

You Need to Build ON A Solid Foundation

Follow SOQL Best practices

Then tune Apex

Then tune Visualforce

Indexes Are Vital for Well-performing SOQL

Without an index the SOQL query may not perform well

Standard indexes already exist on Record_Type_Id, Division,

Created_Date, System_Modstamp (Last_Modified_Date),

Name, Email (for Contacts and Leads), and the unique

Salesforce record ID (Foreign Keys)

Administrators Can Create a Custom Index

Need Additional Indexes?

Salesforce support can create single and two-column custom indexes

on most fields (with the exception of multi-picklists, formula fields that

reference other objects, and Long Text Area/Rich Text Area)

Open a case

- Sample Query

- Bind Variables

- Org ID and user ID who would run the query

- Suggested index - OPTIONAL

If they create an index, then SAVE and document where the index

was created

Will an Index Be Used?

• Whether an index is used is based on the expected number of

records that will be returned.

• A standard index will generally be used:

• If the filter matches less than 30% of the total records, up to 1M records.

• A custom index will generally be used:

• If the filter matches less than 10% of the total records, up to 333K

records.

• OR conditions require that all columns be indexed

Use a Standard Index

Select name from account where Id=‘00530000003hQLJ’

Performs quickly because ID is an standard index

Use a Custom Index

Select name from account where

SLA_Serial_Number__c=‘1234567’

Performs quickly because SLA_Serial_Number__c is a custom

index

Use a Custom Index

Select name from account where SLA_Serial_Number__c=‘’

Doesn’t work because null prevents the index from being used.

Use a Custom Index

Select name from account where SLA_Serial_Number__c IN

:ListOfSerialNums

May work well

if no null variable in ListOfSerialNums

filter matches less than 10% of the total records up to 333,000 records

30% of the total records up to one million records if this was a standard index

(it’s not)

Don’t Use NOT IN

Select name from account where SLA_Status__C NOT IN (‘Valid’)

NOT IN also prevents the index from being used

One (best) Index Will Be Used

Select name from account where SLA_Status__C NOT IN

(‘Processed’) AND SLA_Serial_Number__c=‘1234567’

If one index is not usable, then the best remaining index will be

used.

One (best) Index Will Be Used

Select name from account where SLA_Status__C IN

(‘Processed’) AND SLA_Serial_Number__c=‘1234567’

If all indexes are usable, the best index will be used.

Cross-object Formula Fields Can Prevent Index

Usage

Contact.SLA_Formula__c is a formula field that copies the value

in Account.SLA_Serial_Number__c.

Select name from contact where SLA_Formula__c IN

:ListOfSerialNums

A custom index on Account.SLA_Serial_Number__c cannot be used

in this query.

Use this query instead, where the index can be used:

Select name from contact where Account.SLA_Serial_Number__c IN

:ListOfSerialNums

Denormalizing Data Increases Performance

Select name from contact where Account.SLA_Serial_Number__c

IN :ListOfSerialNums

Solution

Copy SLA_Serial_Number to a field in Contact (don’t use a

formula) and make the field an External Id

OR query for the account IDs with the SLA Serial number first

Query Only The Necessary Fields

SELECT

AccountNumber,AccountSource,Active__c,AnnualRevenue,BillingCity,BillingCountry,BillingPo

stalCode,BillingState,BillingStreet,CreatedById,CreatedDate,CustomerPriority__c,Description,

Fax,Id,Industry,IsDeleted,Jigsaw,JigsawCompanyId,LastActivityDate,LastModifiedById,LastM

odifiedDate,MasterRecordId,Name,NumberOfEmployees,NumberofLocations__c,OwnerId,O

wnership,ParentId,Phone,Rating,ShippingCity,ShippingCountry,ShippingPostalCode,Shipping

State,ShippingStreet,Sic,SicDesc,Site,SLAExpirationDate__c,SLA_Serial_Number__c,SLA__

c,SystemModstamp,TickerSymbol,Type,UpsellOpportunity__c,Website FROM Account

SOSL Performance Best Practices

SOSL queries for the data using a different technique but then

takes the data and adds the where clause using SOQL

- Eg FIND {foo} RETURNING Account (Id WHERE City='Rome') is

analogous to SELECT Id FROM Account WHERE ID IN (<list of Ids

from search>) AND City='Rome’

Follow SOQL best practices for the where clause

Batch Apex

Most common issue is performance of SOQL used in the start()

method.

Avoid the use of non-selective filters in the start() method.

- Queries will perform significantly worse as more data is added.

Don’t add a non-selective filter to filter out a few rows relative to

the overall size of the result set. Instead, use Apex to filter out

rows in the execute() method.

Batch Apex – Start Method Queries

Suppose you have 5M records in Account. You want to process the

80% of those records represented by this query:

- SELECT Id FROM Account WHERE Rating__c IN ('Excellent','Good','Moderate')

Since there is no way to use a selective filter in a query for these

records, this query will not run quickly even if Rating__c is indexed.

As an alternative, use this query in the start method:

- SELECT Id FROM Account

Filter out the unwanted records in the execute method.

Batch Apex – Start Method Queries – Sample Class

global Database.QueryLocator<SObject> start(Database.BatchableContext bc) {

return Database.getQueryLocator('SELECT Id FROM Account');

}

global void execute(Database.BatchableContext bc, List<Account> scope) {

List<Account> actualScope = [SELECT Id, Name, Description FROM Account

WHERE Rating__c IN

('Excellent','Good','Moderate’)

AND Id IN :scope];

for(Account acc : actualScope) { /* do something */ }

}

Batch Apex – Avoid Errors in Bulk DML

global void execute(Database.BatchableContext bc, List<Account>

scope) {

for(Account acc : scope) { /* do something */ }

Database.SaveResult[] results = Database.update(scope,

false);

/* look at results */

}

If an error occurs in this save operation, Salesforce will try to save it one

record at a time.

This performs significantly slower than a bulk save without errors.

Parent-Child Locking

Insert of Contact requires locking the parent Account.

Insert or Update of Event requires locking both the parent Contact and the

parent Account.

Insert or Update of Task requires locking both the parent Contact and

parent Account, if the Task is marked as complete.

Insert of Case requires locking the parent Contact and parent Account.

In objects that are part of a master/detail relationship, updating a detail

record requires locking the parent if roll-up summary fields exist.

Sharing Calculations

“Implicit” Sharing

- Record access built into Salesforce applications

Parent Implicit Sharing (Account only, private sharing model)

- Access to Contact/Opportunity/Case = Read access to parent

account

- not used when sharing on the child is controlled by parent

- when user loses access to a child, need to check all other children

to see if we can delete the parent implicit share

Should we delete Jane’s parent implicit share?

Sharing calculations

impacted by Data Skew

300K unassigned contacts

under account

Private sharing model

Jane has access to contact

Bob Smith

Jane losses access to contact

Should we delete Jane’s

parent implicit share for

Universal Containers?

Can’t code around Data Skew

Universal

Containers

Bob

Smith Fred

Green

Betty

Brown

300K

Contact … ?

X

X

Effects of data skew

Sharing calculations run longer

Concurrent Request Limit error

- Synchronous Apex request starts counting against the limit waiting >

5 sec for lock.

UNABLE_TO_LOCK_ROW error

- Timed out waiting 10 seconds to acquire lock.

- Even if no errors occur, waiting for locks can significantly slow DML

operations.

Recommendations

Consider a public read/write sharing model

- Parent will still be locked. No sharing calculations.

10K children or less

Prevent parent-child data skews

- Detect whether existing accounts already have "reached their limit"

of child records, and create new accounts.

Visualforce – Best Practices

http://developer.force.com/dreamforce/11/session/Blazing-

Fast-Visualforce-Pages

View State

- Filter and Paginate

- Transient keyword

- Simplify component hierarchy

- JavaScript Remoting

Analyzing Performance

Measure performance in the browser first to see if the

problem is client-side or server-side.

- Chrome Developer Tools and the Firebug plugin for Firefox will both

work for this.

After confirming the problem is on the server, use the

Salesforce Developer Console to find areas you can tune.

Analyzing Performance

Example Visualforce Page: DebugPage

Analyzing Performance

In Chrome, press F12 to open Developer Tools.

Use the Network tab to measure performance.

It takes 8.74 seconds to get a response from the server when pressing the “Do BOTH Slow Query and

Callout” button.

Analyzing Performance – Developer Console

Use the Developer Console to analyze server-side performance.

Apex debug logs will be generated for every server request you perform

while the window is open.

Several tools are available in the Developer Console to find performance

hotspots.

Analyzing Performance – Developer Console

1) Open the log for

the slow request.

2) Open the Timeline tab.

3) Identify the slow

portion and click on the

bar. This loads the

relevant log lines into

the Execution Log.

4) Click on a line in

the Execution Log to

show the stack trace

for the slow query on

the left.

Analyzing Performance – Log Levels

The default log levels generate a huge amount of output, most of which

is unnecessary for debugging performance issues.

This also makes the console slower.

Try lowering the log levels so you can look for slow queries and callouts

first.

Analyzing Performance – Heap Dumps

The Developer Console can also be used to create Apex

heaps that help in debugging.

For example, you can use it look at the bind variables for a

query.

Analyzing Performance – Heap Dumps

Analyzing Performance – Heap Dumps

The bind variables will

not show up in the

debug console and may

not be easy to find.

You can set a heap

dump breakpoint to get

the variable values at

the time the query is

run.

Analyzing Performance – Heap Dumps

Set a breakpoint

on the line where

the query is run.

Analyzing Performance – Heap Dumps

The runtime values

of the variables can

be found in the

Symbols tab of the

heap dump viewer.

Analyzing Performance – Useful Tools

Developer Console

Firebug (http://getfirebug.com)

- Web development plugin for Firefox.

Chrome Developer Tools

- Included with Chrome.

Workbench (https://workbench.developerforce.com)

- Good for testing SOQL queries.

Fiddler (http://www.fiddler2.com/fiddler2)

- Windows tool for debugging HTTP traffic, integrates well with IE and Firefox.

Working with Support

SOQL performance

- Open a case with org Id, user Id, SOQL and bind variables.

- Can add custom single and two column indexes.

Record locks

- Provide support the org ID and time frame where the issues

occurred.

- Provide the IDs of affected records if possible.

Useful Links

Architect Core Resources

http://wiki.developerforce.com/page/Architect_Core_Resources

- Guide to Sharing Architecture

- Record Access: Under the Hood

- Best Practices for Deployments with Large Data Volumes

- Asynchronous Processing in Force.com

- VF Performance

Stuart Bernstein

ISV Technical Evangelist

Thomas Harris

LMTS, CCE Production

Support

John Tan

SMTS, CCE Technical

Enablement