Salesforce Apex trigger fires twice on a single record update

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Summary

The Salesforce Apex trigger is firing twice on a single record update, causing unexpected behavior. This issue arises from the trigger updating the record, which in turn triggers the same trigger again, resulting in infinite recursion. To prevent this, it’s essential to understand the trigger context and implement measures to avoid recursive trigger executions.

Root Cause

The root cause of this issue is:

  • The before update trigger is updating a field on the same object that it’s triggered on
  • The update operation is triggering the same trigger again, causing recursion
  • The lack of a condition to prevent recursive executions allows the trigger to fire multiple times

Why This Happens in Real Systems

This issue occurs in real systems due to:

  • Insufficient understanding of Apex trigger behavior and context
  • Inadequate testing of trigger functionality, particularly in regards to recursive executions
  • Poor trigger design, which fails to account for potential recursive trigger executions

Real-World Impact

The real-world impact of this issue includes:

  • Unexpected behavior, such as incorrect data updates or infinite loops
  • Performance degradation, as recursive trigger executions can consume excessive system resources
  • Data inconsistencies, resulting from multiple trigger executions updating the same records

Example or Code (if necessary and relevant)

trigger UpdateOpportunityField on Opportunity (before update) {
    // Check if the trigger is being executed recursively
    if (Trigger.isAfter && Trigger.isUpdate) {
        return;
    }
    for (Opportunity opp : Trigger.new) {
        opp.Custom_Field__c = opp.Amount * 0.1;
    }
}

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Implementing a condition to prevent recursive trigger executions
  • Using trigger context variables, such as Trigger.isAfter and Trigger.isUpdate, to determine the trigger execution context
  • Optimizing trigger design to minimize the risk of recursive executions

Why Juniors Miss It

Juniors may miss this issue due to:

  • Lack of experience with Apex triggers and their behavior
  • Insufficient understanding of trigger context and recursive executions
  • Inadequate testing and debugging of trigger functionality