Missing ability to cast georaphy to geometry when using GeoDjango and PostgresSQL
|Reported by:||corentin.chary@…||Owned by:||nobody|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Description (last modified by aaugustin)
Looking at http://postgis.refractions.net/docs/ch08.html#PostGIS_TypeFunctionMatrix you will see that a lot of functions only work on geometric fields (ie: geography=False).
That means something like Markers.objects.extent() won't work if the coordinate field of Marker have geography set to True because the underlying function (ST_Extent()) only work with geometric fields.
A workaround (if you don't really care about precision) is to cast geography to geometry:
SELECT ST_Extent(coordinates::geometry) FROM markers;
That will perfectly work. However, you can't really do that with django. The best you can do seems to be:
But that's really far from perfect.
Here are some propositions:
- add a way to cast to geometry, that would allow to do: qs.extent(field_name=coordinates__geometry) (the trailing __geometry cast a GeometryField from geography to geometry)
- another way to cast to geometry would be: qs.geometry('coordinates').extent()
- automatically cast geography to geometry if a function only support geometry (hum...)
Change History (2)
comment:1 Changed 3 years ago by aaugustin
- Description modified (diff)
- Needs documentation unset
- Needs tests unset
- Patch needs improvement unset
- Triage Stage changed from Unreviewed to Design decision needed