Calculating the externalId field value using Dataloader CLI

Question

I have a dataloader CLI process setup to import a csv file from a share folder. I am upserting to an object in Salesforce. This object is a junction object called employee training. The junction has two master-detail relation ship to employee and training object. I have a CSV file in share folder with training name and employee id , which I want to upsert to the junction object. I have employee id custom field on junction object which I use as external id for upsert operation.

My problem: I do not have option to add new field or make changes to csv file. WHen I upsert the junction object record with data like below:

CSV:
    Employee    Training    EmployeeId  
    John          Course1     123  
    John          Course2      123

When I run the datalaoder CLI I am unable to create a new junction object with data -( John Course2 123). I guess the problem is I am using the external id as employeeId to do the upsert operation. Since a junction object with external id already exists(John Course1 123) it is unable to add a new junction object(John Course2 123).

What I want:

I want a external id to be defined which is combination of EmployeeId+Training values. I do not have a option to add this external id to my csv file. Is there a way in salesforce I can populate this field before I upsert it to salesforce?

Answer 1

I have a found a solution based on how my business requirement works. I had to only insert new records and it does not matter if there are any duplicates. Since I do not have to update the records I changed the process-config.xml to do only insert operation and made the external id as not unique. This way I could insert new records of the junction object. Hope it helps if some one is looking encounters such a scenario.