Optimize M2M Field

[jonasN5]

This is linked to #4917

django-rest-framework/rest_framework/relations.py

Line 561 in 4c7c693

return relationship.all() if hasattr(relationship, 'all') else relationship

Why can't we just allow some customization at this line? Usually with any toolbox, we provide a best effort default and give the user the option to customize. In this case, the relations will ALWAYS be fetched with .all(). I have a simple case where I need an annotation on each child and so a single query is enough, if done on the ManyRelatedField level. How about making the ManyRelatedField also accept a queryset argument and default to .all() if there is no queryset argument?

[auvipy]

good point, can you share some PoC?

[jonasN5]

class ManyRelatedField(Field):
    ...
    queryset = None

    def __init__(self, child_relation=None, *args, **kwargs):
        self.queryset = kwargs.pop('queryset', self.queryset)
        ...

      

    def get_attribute(self, instance):
        # If a custom queryset has been set, use that before falling back to the best effort
        if self.queryset:
            return self.queryset
        ...

Super simple

Or explicit parameter

    def __init__(self, child_relation=None, queryset=None, *args, **kwargs):
        self.queryset = queryset