you can refer the behavior of data loader.
It shows which fields can be upsertable when upsert mapping.
As you will see, dataloader shows fields whose createable? and updateable? predicates are both false aren't available for upsert.
So, this can apply to update/create through model methods.
Also this means Schema class or Schema::Fields should have methods such as #createable_field_names or #upsertable_field_names
https://github.com/tmkw/sf_model/issues/19
you can refer the behavior of data loader. It shows which fields can be upsertable when upsert mapping. As you will see, dataloader shows fields whose createable? and updateable? predicates are both false aren't available for upsert. So, this can apply to update/create through model methods.
Also this means Schema class or Schema::Fields should have methods such as
#createable_field_namesor#upsertable_field_names