I'm trying to perform an update on our users using Python's Salesforce Bulk interface. Each account has a User ID field (UserID__c, External ID, Unique Case Insensitive) and a Parent ID field (ParentID__c, Lookup(Account)). I am trying to update the Parent ID field on the account using the Bulk API. A sample of the CSV looks like:
"ParentID__r.UserID__c","UserID__c"
123,456
Based on the documentation, I expect that the Parent ID field of user 456 would be updated with the account belonging to the user with User ID 123, but the Parent ID field is always blank. There are no errors when I run the code, but the update for this field never happens. I am able to use the same code to update other field values. Is there something wrong with how I am referencing the lookup relationship?