If you had a model called Flight which has two fields, one called
"total_time", and the other called "distance", you could create a
"speed" field like so:
Flight.objects.extra(select={'speed': 'distance / time'})
Each object will now have a 'speed' field. What if one of those fields
is a result of an annotation? In my particular case, 'distance' is
stored as an attribute of a Route object which is attached to Flight
via Foreign Key.
Flight.objects.annotate(distance=Sum('route__distance')).extra(select=
{'speed': 'distance / time'})
which doesn't work. How can this be achieved? Or is it even possible?
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