Prefetch related fields in API view's querysets

[rmartz]

In the /city/ list view, we currently have a N+1 problem due to using the MapCell object as part of the serialization of City:

The official solution for this appears to be to include the potentially needed related fields as part of the queryset for the parent view, so for CityViewSet we would change it to become

class CityViewSet(...):
    [...]
    queryset = City.objects.all().select_related('map_cell')

We should check if this problem exists for other views or API end points.

[CloudNiner]

Great catch, thanks for writing up an issue!

[fungjj92]

I didn't catch this on any other endpoint, but saw this false positive for indicator list:

Because of the way historic date range is called in params init for appropriate indicators, the requests should in total be made as many times as there are related indicators (tho not ideal).