Child relationship name missing

Question

When I look at some of the Salesforce built-in objects, I notice some lookup field do not have a child relationship name defined - and I cannot set them myself.

For example if I look at the "Campaign Owner" field in the "Campaign" object (via the UI), there is no "Child Relationship Name" displayed (see screenshot). If I edit the field, I cannot manually set a child relationship name.

I am trying to understand whether I can rely on always having a child relationship name - and it seems I cannot. I'd like to understand, then, under what conditions is it not possible to have a child relationship name. Is that specific to Owner fields ? Is there another reason ?

Answer 1

It appears you cannot rely on it, at least not when checking via Schema.ChildRelationship and getChildRelationships()

Describe script used and screenshot below:

List<String> objNames = new List<String>{'User'};
List<Schema.DescribeSobjectResult> dors = Schema.describeSObjects(objNames);

for(Schema.DescribeSobjectResult dor : dors){
    List<Schema.ChildRelationship> childRels = dor.getChildRelationships();
    for(Schema.ChildRelationship c : childRels){
        System.debug(logginglevel.ERROR, 'Child getRelationshipName: ' + c.getRelationshipName());
        System.debug(logginglevel.ERROR, 'Child Object name: ' + c.getChildSObject());
        System.debug(logginglevel.ERROR, 'Child Field: ' + c.getField());
    }
}