Okay, thank you for that answer. That explains a lot.
Is it possible to then search by an identifier and return several patients? The identifier in this case is not intended to be unique, but a way to determine patients coming from a specific mobile device.
EDIT: I have actually come with a workaround, that in the end actually might work better for our project. We intend to use another identifier, that will be the same for several patients. That way, we can search for that identifier, as it would be a complete query, and return all patients we need.