Visualforce and Apex allow developers to extend the Force.com platform and build custom applications. There are, however, some common themes in customer implementations that can adversely affect performance. Join us to learn best practices and debugging techniques for tuning performance of your Apex and Visualforce code.

1. Performance Tuning for Visualforce
and Apex
John Tan, salesforce.com, @johntansfdc
Thomas Harris, salesforce.com

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3. Your company uses
Salesforce/Force.com …

4. You are a developer or
architect…

5. Your Visualforce pages and Apex
classes are slower than you’d
like…

6. You need to find and fix the
issues…

7. Agenda
1. Record lock contention
2. Building efficient queries
3. Batch Apex
4. Visualforce
5. Apex and CPU limit
6. Debugging Tips and Tricks

8. John C. Tan
Lead Member of Technical Staff
Customer Centric Engineering
@johntansfdc

9. Thomas Harris
Lead Member of Technical Staff
Customer Centric Engineering

10. Architect Core Resource page
• Featured content for architects
• Articles, papers, blog posts,
events
• Follow us on Twitter
Updated weekly!
http://developer.force.com/architect

11. Build On A Solid Foundation
1. Data model & queries
2. Then tune Apex
3. Then tune Visualforce

12. By a show of hands…
How many of you have gotten these errors?
UNABLE_TO_LOCK_ROW

13. Record Lock Contention / Data
Skew

14. Parent-Child Locking

15. 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, inserts require locking the
master. Updates will also lock the master if a roll-up summary is present.
▪ In objects that are part of a lookup relationship where the lookup is set to Clear on
delete, inserts require locking the target lookup record. Updates will lock the target
lookup record if the value of target changes.

16. Parent implicit sharing
Access to Contact/Opportunity/Case = Read access to
parent Account
Account:
Universal
Containers
Contact:
Bob
Smith

17. Data skew impacts DML operations
Universal
Trigger/RSF
Containers
?
Bob
Smith
Fred
Green
Betty
Brown
…
300K
Contact
New
Contact

18. Result Of Longer Sharing Calculations
▪ DML operations run longer
▪ Concurrent Request Limit errors
▪ UNABLE_TO_LOCK_ROW errors

19. Key Takeaways
✓ Prevent parent-child data skews
✓ 10K or less children
✓ Public read/write sharing model = No sharing calculations

20. Building Efficient Queries

21. What is the Force.com query optimizer?
Generates the most efficient query based on:
▪ Statistics
▪ Indexes / Skinny Tables
▪ Sharing

22. Best practice: One+ selective filter per query

23. Selective filters: Four components
1. Filters - add filters to reduce data
2. Operators - avoid 2 inefficient filter operators
3. Thresholds - filter meets selectivity threshold (efficient to
use index)
4. Index Creation - index the filter field

24. Fields that often make good filters
▪ Date fields
▪ Picklists
▪ Fields with wide and even distribution of values

25. Non-deterministic formula fields aren’t good filters
Can’t index
For example:
▪ References related object
▪ CASE(MyUser__r.UserType__c,1,”Gold”,”Silver”)
▪ Create separate field and use trigger to populate
Force.com SOQL Best Practices: Nulls and Formula Fields

26. Avoid negative operators
Query for reciprocal values instead
✖ Status != 'closed'
✔ Status IN ('open', 'in progress')

27. Avoid filters with a leading % wildcard
CONTAINS or LIKE ‘%searchstring%’
✖ CONTAINS ('district') / LIKE '%district%'
✔ STARTS WITH ('district') / LIKE 'district%'

28. Standard fields with indexes
▪ Id
▪ Name
▪ OwnerId
▪ CreatedDate
▪ SystemModstamp
▪ RecordType
▪ Master-detail fields
▪ Lookup fields

29. Custom indexes
• Discover common filter conditions
• Determine selective fields in those conditions
• Request custom indexes

30. Standard index selectivity threshold
A standard index is selective if it returns:
▪ < 30% of the first 1 million records
▪ < 15% of returned records after the first 1 million records
▪ No more than 1 million records

31. Standard index selectivity threshold
SELECT Id FROM Account WHERE CreatedDate >
'2013-01-01' AND CreatedDate < '2013-11-01'
For 750,000 Account records
▪ < 30% of the first 1 million records
▪ 750,000 x .30 = 225,000

32. Standard index selectivity threshold
For 3,500,000 Account records
▪ < 30% of the first 1 million records
▪ < 15% of returned records after the first 1 million records
▪ (1,000,000 x .30) + (2,500,000 x .15) = 675,000

33. Standard index selectivity threshold
Over 5,600,000 Account records
▪ No more than 1 million records
▪ 1,000,000

34. Custom index selectivity threshold
A custom index is selective if it returns:
▪ < 10% of the first 1 million records
▪ < 5% of returned records after the first 1 million records
▪ No more than 333,333 records

35. A filter condition is selective when …
… it uses an optimizable operator
… it meets the selectivity threshold
… selective fields have indexes

36. AND conditions
WHERE FirstName__c = 'Jane' AND LastName__c = 'Doe' AND
City__c = 'San Francisco'
Step 1 – Allow each index to still be considered if they return < 2X selectivity
threshold
Step 2 – INTERSECTION of all indexes must meet *selectivity threshold
Step 3 – Use composite index join to drive query
*If all indexes are standard indexes, use standard index selectivity threshold. Otherwise, use the custom index selectivity
threshold

37. AND conditions
Composite index join – MyUser object 100,000 total records

38. AND conditions
Composite index join – MyUser object 100,000 total records

39. 2-column index
For this simple example, it makes more sense to have Customer Support create a 2-column index.

40. OR conditions
WHERE FirstName__c = 'Jane' OR LastName__c = 'Doe' OR
City__c = 'San Francisco'
Step 1 – Each field must be indexed and meet selectivity threshold
Step 2 – UNION of all the indexes must meet *selectivity threshold
Step 3 – Use union to drive query
*If all indexes are standard indexes, use standard index selectivity threshold. Otherwise, use the custom index selectivity
threshold

41. OR conditions
Union - MyUser object 100,000 total records

42. Tell me more…
Webinar: Inside the Force.com Query Optimizer

43. Key takeaways
✓ Queries should contain at least one selective filter
✓ A filter is selective if…
✓ the field is indexed
✓ the filter does not use an inefficient operator
✓ the filter meets the selectivity theshold

44. Batch Apex

45. Batch Apex
▪ The most common performance issue in Batch Apex is poor
performing queries in the start() method.
▪ Make sure you are using a selective filter in the start method.

46. Batch Apex start() method
▪ 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')
▪ As an alternative, use this query in the start() method:
• SELECT Id FROM Account
▪ Filter out the unwanted records in the execute() method.

47. Batch Apex start() method example
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 */ }
}

48. Visualforce

49. Visualforce
▪ In general, follow SOQL and Apex best practices.
▪ Visualforce-specific issues tend to be caused by complex pages with
large numbers of components, which in turn have a very large view
state.

50. Visualforce
▪ Techniques to reduce view state overhead:
• Filter and paginate results.
• Use the transient keyword
• Simplify the component hierarchy on the page.
• Use Javascript Remoting.

51. Apex and CPU Limits

52. Apex CPU Limits
▪ In Winter ‘14 Apex now has a CPU time limit rather than a
script statement limit.
▪ In general existing Apex code will be well under this limit.
▪ There are two main pitfalls to avoid that can use up large
amounts of CPU time with a low number of script
statements.

53. Apex CPU usage pitfalls
▪ String concatenation: doing large numbers of “+” operations with large
strings.
• Example:
String html = “<html>”;
html += “<body>”
html += …
• Avoid building huge strings this way using Apex.
• Use System.JSON and System.XmlStreamWriter if you need to build JSON or
XML output.
▪ Running complex regular expressions on large strings.

54. Debugging Tips and Tricks

55. Troubleshooting Methodology
▪ In general it’s a good idea to measure performance in the
browser first.
• Chrome Developer Tools is excellent for this.
▪ Once you know the problem is on the server-side, use the
Developer Console to dig in further.
• Check the usual suspects first:
– SOQL
– Callouts

56. Apex Debug Levels
▪ When troubleshooting performance issues, the default log
levels can generate a lot of noise.
▪ Set the log levels for everything to INFO initially, raise as
necessary.
• Go to Debug > Change Log Levels in the Developer Console to do this.

57. Working With Support
▪ Support can help with SOQL performance issues and can
create 1-column and 2-column custom indexes.
• Open a case and specify the organization ID, user ID, SOQL and bind
variables.
▪ For record locking issues, specify the organization ID, time
frame where the issue happened, and the IDs of affected
records if possible.

58. Summary

59. Key Takeaways
✓ Prevent parent-child data skews
✓ Queries should contain at least one selective filter
✓ Most common issue is performance of the start() method
SOQL
✓ Reduce view state in your Visualforce pages

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