Django admin, exception in queryset when using values() before annotate

[essadek]

class AppModel(models.Model):

    nbr = models.BigIntegerField(blank=True, null=True)
    region = models.ForeignKey(AppWilaya,blank=True, null=True)
    date_preorder = models.DateField(blank=True, null=True)
    id = models.IntegerField(primary_key=True,blank=True, db_column='dummy_id')

class AppModelAdmin(admin.ModelAdmin):
....
def queryset(self, request):
        qs = super(AppModelAdmin, self).get_queryset(request)  
        qs=qs.values("region").annotate(total=Sum( 'nbr'))

Exception Value: 'dict' object has no attribute '_meta'
Exception Location: [PATH_TO]\lib\site-packages\django\contrib\admin\util.py in lookup_field, line 242

Note when removing .values("region") the exception doesn't occur.

[Simon Charette]

It's not clear to me what you're trying to accomplish here, the admin requires a normal queryset not a value one.

Are you trying to select only the region field? In this case you should use ​only and not values.

qs = qs.annotate(total=Sum('nbr')).only('region')

[essadek]

What is needed is aggregation, means sum(nbr )group by region:

SELECT region, \
          SUM(nbr) AS  total\
          FROM  app_model\
          GROUP BY  region\

Never seen usage of "only()" In all search I've done on aggregation in Django Admin.

[Tim Graham]

Please see TicketClosingReasons/UseSupportChannels for other ways to get help with constructing proper queries besides reading the documentation. The information you've provided so far suggests problems in your own code, not in Django itself.