python - Django - Multi-table inheritance - reverse relation to SubClass -


i appreciate following problem. lets use models django documentation illustrate situation.

models.py

from django.db import models  class place(models.model):     owner = djangomodels.foreignkey('owner', related_name='places')     objects = passthroughmanager.for_queryset_class(placequeryset)()  class restaurant(place):     ... members ...     objects = passthroughmanager.for_queryset_class(restaurantqueryset)()  class pub(place):     ... members ...     objects = passthroughmanager.for_queryset_class(pubqueryset)()  class owner(models.model):     ... members ...

queryset.py

class placequeryset(djangomodels.query.queryset):     .. common place filters ...  class restaurantqueryset(placequeryset):     .. restaurant specific filters ...  class pubqueryset(placequeryset):     .. pub specific filters ...

so can see above have 1 base model 'place' , 2 sub models 'restaurant' , 'pub'. base model 'place' has link 'owner' object. querysets (placequeryset, restaurantqueryset, pubqueryset) have same inheritance hierarchy models (place, restaurant, pub).

the challenge having somehow retrieve pubqueryset containing pub objects linked owner....

i know 1 way need add owned_by(owner) filter pubqueryset , call following:

pub.objects.owned_by(owner)

but has performance issues because '.objects' not use prefetched results , hits db.

my thoughts:

when call 

# owner instance of owner class >>owner.places.all()

it returns

placequeryset[<place object ><place object ><place object >....]

but how 

pubqueryset[<pub object ><pub object >]

???

i know select_subclasses() method django-model-utils(1) can downcast objects in queryset if this

# owner instance of owner class >>owner.places.select_subclasses('pub')

i placequeryset instances of pub class

placequeryset[<pub object ><pub object >]

but still receive placequeryset , not pubqueryset...

thank help

jano


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