This document provides an overview and agenda for a session on debugging Apex triggers in Salesforce. It discusses common trigger problems like cascading triggers, governor limits, and null reference errors. It also outlines tools for working with triggers and provides examples of trigger use cases. The session aims to explore these common errors and how to solve them through code examples and using the Salesforce debug logs.

1. Apex Trigger Debugging
Solving the Hard Problems
Cory Cowgill, The Warranty Group
@Cory Cowgill

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3. Apex Trigger Debugging
• Apex Triggers are a powerful feature of the Salesforce platfrom. They allow for
tremendous flexibility in building custom applications on the platform. Because they
execute within the database layer of the platform they can be used for multiple use
cases across an application.
• This flexibility can be a double edged sword. When you build triggers you are
exposing additional risk for errors into your application. During this session we will
be exploring some of these common errors and how you can solve for them.

4. Agenda
 Apex Triggers Overview
• Technical Scope of Session
• Basics of Apex Triggers
• Tools to work with Triggers
 Common Trigger Problems & Resolutions
• Cascading Triggers
• Apex Governor Limits
• Null Reference Errors
• Too Many SOQL Queries

5. Technical Scope
 This is a Apex Trigger Session!
• Apex Trigger Code
• Apex Classes
• Stack Traces
• Trigger Execution Context
 This session will be code and stack trace heavy.
• Code not Clicks

6. Basics of Apex Triggers
 Execute at the database layer via DML (Data Manipulation Language)
• Insert, Update, Upsert, Delete, Un-Delete
• Before, After
 What does this mean?
• Regardless of invocation point they will fire
• Standard Pages, Visualforce Pages, API calls, etc.

7. Basics of Apex Triggers
 Order of Execution
• 1. Before Trigger Execution
• 2. System Validation Rules Execution
• 3. Record Saved in Memory (Not DB) (ID Assigned)
• 4. After Trigger Execution
• 5. Assignment Rules
• 6. Auto-Response Rules
• 7. Workflow Rules (Trigger Step 1 If Field Update)
• Full Order:
http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_triggers_or
der_of_execution.htm

8. Trigger Tools
 Force.com IDE
• Anonymous Apex
• Result Logs
• Unit Tests

9. Trigger Tools
 Salesforce Platform Debug Logs
• Stack Traces
• Per User Debugging

10. Apex Governor Limits

11. Example Use Cases
1. When an Opportunity is “Closed Won”, automatically generate a Invoice.
2. When an Opportunity Product is added to an Opportunity, automatically
update the Opportunity Amount.
3. When an Invoice is generated, automatically link it to the Account and
update the Account Client Lifetime Revenue.
4. When an Account is set to start invoice setup, automatically link the
mailing Contact to the Invoices.

12. Understand Your Data Model – Schema Builder

13. Complex Problem #1 – Cascading Triggers
 Definition
• A trigger updates another record, which updates another record, which eventually
consumes all the trigger resources forcing an error

14. Complex Problem #1 – Cascading Triggers

15. Complex Problem #1 – Cascading Triggers
 Resolution
• There is no silver bullet for this issue
• Static Variables can be used to prevent recursive or cascading logic from
happening
• Reducing the number of Apex triggers and following best practices can mitigate
this issue
• Logic can be moved to Batch Apex if it is too large or complex

16. Complex Problem #2 – Null Reference Errors
 Definition
• A trigger attempts to access a instance of an object that is empty
• A trigger attempts to access a property of an object that is empty
• This is common error amongst all programming languages
• Manifests itself in Apex the same as other languages (Java, etc)

17. Complex Problem #2 – Null Reference Errors

18. Complex Problem #2 – Null Reference Errors
 Resolution
• Perform null checks in your Apex code
• Ensure SOQL is pulling all fields referenced in your Apex code, consider using
Apex DAO objects to encapsulate queries
• Configure Objects to have default (non-null) values

19. Complex Problem #3 – Too Many SOQL Queries
 Definition
• In a given Apex Trigger context, you cannot execute more than 100 SOQL
Queries
• This is typically due to either simple for loops executing SOQL, or more complex
cascading trigger logic.

20. Complex Problem #3 – Too Many SOQL Queries

21. Complex Problem #3 – Too Many SOQL Queries
 Resolution
• Remove SOQL from for loops, while loops, or recursively called methods
• For large query logic, consider moving the logic into Apex Batch instead of an
Apex trigger
• Condense Child-Parent into one Query
• Make sure that triggers are bulkified

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