CODEWITHSUNDEEP
pythondjangodjango-modelsormdjango-queryset
Arun Laxman
Arun Laxman

Reputation: 386

How to build a queryset in a specific order in Django

I'm trying to list profiles of users. I want to list them in such a way that profiles with same city of the user should come first, then next priority should be state, then country, and finally, rest of the profiles. This is what I have tried. model

class Profile(models.Model):
    uuid = UUIDField(auto=True)
    user = models.OneToOneField(User)
    country = models.ForeignKey(Country, null=True)
    state = models.ForeignKey(State, null=True)
    city = models.ForeignKey(City, null=True)

views.py current_user = Profile.objects.filter(user=request.user)

profiles_city = Profile.objects.filter(city=current_user.city)
profiles_state = Profile.objects.filter(state=current_user.state)
profiles_country = Profile.objects.filter(country=current_user.country)
profiles_all = Profile.objects.all()
profiles = (profiles_city | profiles_state | profiles_country | profiles_all).distinct()

But it is yielding the same result as Profile.objects.all()

Please help me. thanks in advance

Upvotes: 2

Views: 1059

Answers (1)

heemayl
heemayl

Reputation: 42037

You need the order_by method of QuerySet that orders objects based on passed parameters; this is done on database:

Profile.objects.order_by(
    'current_user__city',
    'current_user__state',
    'current_user__country',
)

Edit:

If you want to sort by the city, state and country names of the logged in user, you can do this on the Python level, using sorted, and a custom key callable:

from functools import partial


def get_sort_order(profile, logged_in_profile):
    # This is a simple example, you need to filter against
    # the city-state-country combo to match precisely. For
    # example, multiple countries can have the same city/
    # state name.

    if logged_in_profile.city == profile.city: 
        return 1 
    if logged_in_profile.state == profile.state: 
        return 2 
    if logged_in_profile.country == profile.country: 
        return 3
    return 4 

logged_in_profile = request.user.profile  # logged-in user's profile
get_sort_order_partial = partial(get_sort_order, logged_in_profile=logged_in_profile)

sorted(
    Profile.objects.all(),
    key=get_sort_order_partial,
)

Doing the same on the database level, using Case and When to have a Python if-elif-else like construct:

from django.db.models import Case, When, IntegerField

Profile.objects.order_by( 
    Case( 
        When(city=logged_in_profile.city, then=1), 
        When(state=logged_in_profile.state, then=2), 
        When(country=logged_in_profile.country, then=3), 
        default=4, 
        output_field=IntegerField(), 
    ) 
)

This will result in a queryset and also has the added advantage of being faster as all the operations would be done on the database (SELECT CASE WHEN ...).

Upvotes: 4

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