What set of fields gets returned from .getSObject(fieldName)?

Question

I'm working on a function that does a series of .getSObject() calls from an Account record to get three fields from one of the related records.

The issue I'm having is one of the fields returns a SObject row was retrieved via SOQL without querying the requested field error when doing the .get(), but the other two work fine.

This is what each call looks like, with a different field retrieved each time (account is an Account record that gets passed in):

SObject r = account.getSObject('Related1__r');
String test = (String) r.getSObject('Related2__r').get('fieldName__c');

It's not clear from Salesforce documentation what the object returned from .getSObject() and why it works fine for two fields but fails for the third. I can do a dynamic SOQL query to retrieve the same record that should be returned from the Related2__r .getSObject() call and then do a .get() on the exact same field but when I try to do the code snippet above for that particular field, it fails. It seems as if the .getSObject() only retrieves a subset of the fields, and in my case it doesn't include the field I need.

Answer 1

The getSObject method returns all fields in memory. The following two lines should function identically:

SObject related = account.Related2__r;
// or
SObject related = account.getSObject('Related2__r');

If you are getting the error:

SObject row was retrieved via SOQL without querying the requested field

It means your SOQL does not include Related2__r.RequestedField__c. Double check your top level SELECT clause. Every field included in the below SELECT clause would carry over:

SELECT
    Related2__r.Field1__c,
    Related2__r.Field2__c,
    Related2__r.Field3__c
FROM Account

However, if you tried to reference Related2__r.Field4__c, you would encounter this error.