Database error using distance() in GeoDjango

Given the following (simplified) models:

from django.contrib.gis.db import models

class City(models.Model):
    center = models.PointField(spatial_index=True, null=True)
    objects = models.GeoManager()

class Place(models.Model):
    city = models.ForeignKey(City, null=True)
    lat = models.FloatField(null=True)
    lng = models.FloatField(null=True)
开发者_JAVA百科    objects = models.GeoManager()

Forgetting for the moment that the lat/lng in Place should be moved to a PointField(), I am trying to look through all of the Places and find the closest city. Currently, I am doing:

from django.contrib.gis.geos import Point

places = Property.objects.filter(lat__isnull=False, lng__isnull=False)
for place in places:
    point = Point(place.lng, place.lat, srid=4326) # setting srid just to be safe
    closest_city = City.objects.distance(point).order_by('distance')[0]

This results in the following error:

DatabaseError: geometry_distance_spheroid: Operation on two GEOMETRIES with different SRIDs

Assuming that the SRIDs were not defaulting to 4326, I included srid=4326 in the above code and verified that all of the cities have City.center has an SRID of 4326:

In [6]: [c['center'].srid for c in City.objects.all().values('center')]
Out[6]: [4326, 4326, 4326, ...]

Any ideas on what could be causing this?

UPDATE:

There seems to be something in how the sql query is created that causes a problem. After the error is thrown, looking at the sql shows:

In [9]: from django.db import connection
In [10]: print connection.queries[-1]['sql']
SELECT (ST_distance_sphere("model_city"."center", 
    ST_GeomFromEWKB(E'\\001\\001...\\267C@'::bytea))) AS "distance", 
    "model_city"."id", "model_city"."name", "listing_city"."center" 
    FROM "model_city" ORDER BY "model_city"."name" ASC LIMIT 21

It looks like django is turning the point argument of distance() into Extended Well-Known Binary. If I then change ST_GeomFromEWKB to ST_GeomFromText everything works fine. Example:

# SELECT (ST_distance_sphere("listing_city"."center",
          ST_GeomFromText('POINT(-118 38)',4326))) AS "distance", 
          "model_city"."name", "model_city"."center" FROM "model_city" 
          ORDER BY "listing_city"."name" ASC LIMIT 5;

     distance     |    name     |                       center                       
------------------+-------------+----------------------------------------------------
 3124059.73265751 | Akron       | 0101000020E6100000795DBF60376154C01CB62DCA6C8A4440
  3742978.5514446 | Albany      | 0101000020E6100000130CE71A667052C038876BB587534540
 1063596.35270877 | Albuquerque | 0101000020E6100000CC0D863AACA95AC036E7E099D08A4140

I can't find anything in the documentation that speaks to how GeoQuerySet.distance() translates into SQL. I can certainly use raw SQL in the query to get things to work, but would prefer to keep everything nicely in the Django framework.

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i think this error : "Operation on two GEOMETRIES with different SRIDs"

"geometry_columns" table on your database is set different srid between your table name to process

***** you should change it yourself