django-REST: Nested relationships vs PrimaryKeyRelatedField

Question

Is it better to use nested relationships or PrimaryKeyRelated field if you have lots of data?

I have a model with deep relationships.
For simplicity I did not add the colums.

Model:

Usecase:

1. User creates 1 Workoutplan with 2 Workouts and 3 WorkoutExercises.
2. User creates 6 Sets for each WorkoutExercise/Exercise.
3. User starts workout > new FinishedWorkout is created
4. User does first exercise and enters the used weights > new FinishedWorkoutExercise with FinishedSet is created

Question:

I want to track the progression for each workoutplan > workout > exercise. So with time the user may have finished dozens of workouts therefore hundreds if sets are already in the database.

If I now use nested Relationships I may load a lot of data I don't need. But if I use PrimaryKeyRelatedFields I have to load all the data I need separately which means more effort in my frontend.

Which method is preferred in such a situation?

Edit:
If I use PrimaryKeyRelatedFields how do I distinguish if e.g. Workouts in Workoutplan is an array with primary keys or an array with the loaded objects?

Answer 1

If you use PrimaryKeyRelatedField, you'll have a big overload to request the the necessary data in frontend

In your case, I would create specific serializers with the fields you want (using Meta.fields attribute). So, you won't load unecessary data and the frontend won't need to request more data from backend.

I can write a sample code, if you need more details.