We have many occurrences in the code where we try to determine the class affiliation (a.k.a., isInstanceOf ) of a pointer to a DocumentSource, and there are at least 3 ways to do that:

1. dynamic cast the pointer to the target type and check if it fails (at least 36 times in master)
2. compare pointer->getSourceName() with a string constant (at least 18 times in master)
3. compare pointer->getId() (introduced by SERVER-99019) with an integer constant (at least 2 times in master)

It would be nice if we had some consistency. Out of 3 methods, the string comparison seems least efficient.