Operations That Don't Invoke Triggers - Cascading delete operations

Question

I was going through documentation about Operations That Don't Invoke Triggers and got confused with Cascading delete operations. Records that did not initiate a delete don't cause trigger evaluation statement.

In our org we use three level cascade delete in various places and never noticed this behavior. Triggers of all the three objects are evaluated every time.

In before trigger of every trigger, I do this:

public static void cleanupChildren(map<Id, Object1__c> mapOld) {
    delete [Select Id FROM Object2__c WHERE Parent__c IN :mapOld.keySet()];
}

I can confirm that all the three triggers are evaluated when the delete operation was initiated by Object1__c. As per the documentation triggers of Object2__c and Object3__ should not be evaluated as they didn't initiate delete operation.

What am I missing here? Did I misinterpret the definition of Cascade deletion?

Answer 1

In your use case, you are explicitly calling a Delete DML operation on the child Object2 and that will execute the before/after delete triggers on Object2

But, imagine that the trigger of Object1 did not do an explicit delete call on Object2 children. When Object1 (parent) is deleted by user action (or API/Apex DML), the children are cascaded deleted by SFDC and their before/after delete triggers will not be fired

What the documentation is trying to say is that a behind-the-scenes cascade delete will not automatically trigger before/after delete triggers on the targets of the cascade deletion

Cascade delete is on by default for master-detail relationships. If the master is deleted, the children are implicitly (cascade) deleted and their triggers will not be fired.