refresh_from_db() got an unexpected keyword argument 'fields'

[juanjgarcia]

Given this code sample

only_fields = (
    'foo', 'bar', 'api_request'
)
active_workers = (
    worker_api.active_workers()
    .exclude(api_request=None)    
    .only(*only_fields)
)
for worker in active_workers:
    print('foobar')

When evaluating active_workers in the iterable, the following is thrown:

refresh_from_db() got an unexpected keyword argument 'fields'

worker_api.active_workers() return a Queryset of Worker objects which are django-polymorphic classes from a Provider class.

We've been able to get around this buy using prefetch_related('api_request') instead of explicit fields using .only. This approach returns too much data, but is still performant.

This looks like a bug when prefetching specific fields, which from the docs seems to be supported.

Any help welcome! Thanks

Django 1.11.29 Django Polymorphic 2.1.2 Python 2.7