Take these models:
class Rocket(Model):
...
class Flight(Model):
rocket = ForeignKey(Rocket)
start_time = DateTimeField(...)
If I want to get start times of the latest flight for every rocket, that is simple:
>>> Flight.objects.values('rocket').annotate(max_start_time=Max('start_time'))
<QuerySet [
{'rocket': 3, 'max_start_time': datetime.datetime(2019, 6, 13, 6, 58, 46, 299013, tzinfo=<UTC>)},
{'rocket': 4, 'max_start_time': datetime.datetime(2019, 6, 13, 6, 59, 12, 759964, tzinfo=<UTC>)},
...]>
But what if instead of max_start_time
I wanted to select IDs of those same Flights?
In other words, I want to get the ID of the latest Flight for every rocket.