I think this might be a bug in source code, but before I report a
ticket I thought I would ask just to ensure it's not me doing
something wrong/stupid.
In brief, I have a (MySQL) database table containing latitude and
longitude columns. I am finding records from this table and sorting
them based on distance, and to do this I'm adding a custom column in
the select statement using the extra() QuerySet function.
So here's the relevant code for this part:
entries = Entry.objects.filter(type='country')
entries = entries.extra(select={'distance': "SQRT(POW((locations.lat-
%s),2) + POW((locations.lon-%s),2))"}, select_params=(str(centerLat),
str(centerLng)))
entries = entries.extra(order_by = ['distance'])[:100]
In a nutshell, this code defines a custom column "distance" and uses
some MySQL numeric functions to calculate a hypotenuse to get the
distance value. The result set is ordered by this column. This works
great.
Now for the issue...when I serialize this code as follows:
from django.core import serializers
json_serializer = serializers.get_serializer("json")()
json_serializer.serialize(entries, ensure_ascii=False,
stream=response, fields=('title','lat','lon','distance'))
The problem being that the "distance" column does not end up getting
included in the json output. The other columns are included, however,
no problem.
I have even inspected the queryset in entries an confirmed that each
object does in fact contain a distance attribute, as a float, which is
set properly.
So....finally to my question...is there an issue of some kind with the
way the serializer handles extra fields, or am i just doing it wrong?
FYI i'm on the latest release Django version 1.0-beta_1-SVN-8539.
Thanks for any help or suggestions you guys can provide!
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