id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
22830	GeoDjango dwithin errors when using django.contrib.gis.measure.D	django@…	nobody	"First off, I started a StackOverflow thread [http://stackoverflow.com/questions/24194710/geodjango-dwithin-error-argument-of-type-geoqueryset-is-not-iterable here] but haven't come up with an answer yet. I think there may be a bug in Django somewhere.

Versions: Python 2.7.6, Django 1.6.5, Postgres 9.3.4, PostGIS 2.1.3, psycopg2 2.5.3 on RHEL 6.5

Here's the model I'm using:

{{{
#!python
class Location(models.Model):
    name = models.CharField(max_length=255)
    geometry = models.MultiPolygonField(blank=True, default=None, null=True)
    objects = models.GeoManager()  # override the default manager with a GeoManager instance
    parent = models.ForeignKey('self', blank=True, default=None, null=True)

    def __unicode__(self):
        return self.name
}}}

This query should work [https://docs.djangoproject.com/en/1.6/ref/contrib/gis/geoquerysets/#std:fieldlookup-dwithin according to the docs]:

{{{
#!python
touching_locations = Location.objects.filter(geometry__dwithin=(location.geometry, D(km=5)))
logging.debug(type(touching_locations))
logging.debug(len(touching_locations))
}}}

But it doesn't. The first debug call works, but the second throws a `ValueError`:

{{{
<class 'django.contrib.gis.db.models.query.GeoQuerySet'>
ValueError: Only numeric values of degree units are allowed on geographic DWithin queries.
}}}

If I make a small change by changing `D(km=5)` to `5`:

{{{
#!python
touching_locations = Location.objects.filter(geometry__dwithin=(location.geometry, 5))
logging.debug(type(touching_locations))
logging.debug(len(touching_locations))
}}}

All of a sudden it works. The output I get is this:

{{{
<class 'django.contrib.gis.db.models.query.GeoQuerySet'>
54
}}}

Is there a bug somewhere in Django? Am I misunderstanding how to use `D`? Are the Django docs incorrect? Is something else going on here? I appreciate any help I can get. Thanks!"	Bug	closed	GIS	1.6	Normal	invalid			Unreviewed	0	0	0	0	0	0