Paginating a queryset with a distance lookup fails due to unhashable type Distance

[Illia Volochii]

There is a model with a location = models.PointField() field.

Django 2.2.17 fails to paginate such a queryset because of TypeError: unhashable type: 'Distance':

from django.contrib.gis.geos import Point
from django.contrib.gis.measure import Distance
from django.core.paginator import Paginator
from django.db.models import Case, IntegerField, Q, Value, When

point = Point(0, 0)
cities = City.objects.annotate(
    relative_distance=Case(
        When(Q(location__distance_lte=(point, Distance(mi=100))), then=Value(100)),
        default=Value(1000),
        output_field=IntegerField(),
    ),
)
Paginator(cities, 10).page(1)

This code works well with Django 1.11 and the latest development version.

For those who have faced this bug too, it is possible to use Distance(mi=100).m that is a hashable float in the lookup.

I attached a file with a full exception taceback.

Thanks,
Illia

[Claude Paroz]

MeasureBase is clearly missing a __hash__ method.

[Mariusz Felisiak]

Paginator issue is fixed, but you can still encounter this issue when grouping by annotation with Distance().

[Mariusz Felisiak]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In bef6f758:

Fixed #32358 -- Fixed queryset crash when grouping by annotation with Distance()/Area().

Made MeasureBase hashable.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 8dcb8b9:

[3.2.x] Fixed #32358 -- Fixed queryset crash when grouping by annotation with Distance()/Area().

Made MeasureBase hashable.

Backport of bef6f7584280f1cc80e5e2d80b7ad073a93d26ec from master

[Illia Volochii]

Thanks, Mariusz. Could you please backport the commit to 2.2.x?

[Tim Graham]

Per our ​supported versions policy, 2.2 is only receiving fixes for security and data loss issues.