Apex Trigger DebuggingApex Trigger DebuggingSolving the Hard Problems

Cory Cowgill, The Warranty Group

@Cory Cowgill

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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.

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

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

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.

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_order

_of_execution.htm

Trigger Tools Force.com IDE

• Anonymous Apex

• Result Logs

• Unit Tests

Trigger Tools Salesforce Platform Debug Logs

• Stack Traces

• Per User Debugging

Apex Governor Limits

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.

Understand Your Data Model – Schema Builder

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

Complex Problem #1 – Cascading Triggers

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

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)

Complex Problem #2 – Null Reference Errors

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

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.

Complex Problem #3 – Too Many SOQL Queries

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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