[Django]-GeoDjango inteprets MultiPolygon as LinearRing

Each polygon of a MultiPolygon should still form a closed linestring. Your data is probably malformed or corrupted.

You can try to fix this by using ST_MakeValid.

UPDATE aeroway_polygon
SET geom = ST_Multi(ST_CollectionExtract(ST_Makevalid(geom), 3))
WHERE ST_IsValid(geom) = false;

Note that I didn’t test this query, I found it here on gis.stackexchange.

Polygons by definition are closed geometries, which means that the first and last Point must be the same exact Point.
For Multipolygons the same principle exists, hence every Polygon of a Multipolygon must be closed and there must not be “free” edges inside the geometry.

If you check your dataset you will find that some of those LineStrings are not closing.

@AntoinePinsard gives a good PostGIS solution.
In GeoDjango version >= 1.10, MakeValid exists as a database function and we can use it on queries:

AerowayPolygon.objects.all().update(geom=MakeValid('geom'))

If your Django version < 1.10, I have a set of answers on how to create a custom database function and use it as in the example above:

• How to make/use a custom database function in Django
• Equivalent of PostGIS ST_MakeValid in Django GEOS:

from django.contrib.gis.db.models.functions import GeoFunc

class MyMakeValid(GeoFunc):
      function='ST_MakeValid'

AerowayPolygon.objects.all().update(geom=MyMakeValid('geom'))