Django query: Count and Group BY

Question

I have a query that I'm trying to figure the "django" way of doing it: I want to take the last 100 calls from Call. Which is easy: calls = Call.objects.all().order_by('-call_time')[:100]

However the next part I can't find the way to do it via django's ORM. I want to get a list of the call_types and the number of calls each one has WITHIN that previous queryset i just did. Normally i would do a query like this: "SELECT COUNT(id),calltype FROM call WHERE id IN ( SELECT id FROM call ORDER BY call_time DESC LIMIT 100 ) GROUP BY calltype;"

I can't seem to find the django way of doing this particular query.

Here are my 2 models:

class Call( models.Model ):
    call_time = models.DateTimeField( "Call Time", auto_now = False, auto_now_add = False )
    description = models.CharField( max_length = 150 )
    response = models.CharField( max_length = 50 )
    event_num = models.CharField( max_length = 20 )
    report_num = models.CharField( max_length = 20 )
    address = models.CharField( max_length = 150 )
    zip_code = models.CharField( max_length = 10 )
    geom = models.PointField(srid=4326)
    calltype = models.ForeignKey(CallType)

    objects = models.GeoManager()

class CallType( models.Model ):
    name = models.CharField( max_length = 50 )
    description = models.CharField( max_length = 150 )
    active = models.BooleanField()
    time_init = models.DateTimeField( "Date Added", auto_now = False, auto_now_add = True )

    objects = models.Manager()

Answer 1

With django 1.1.1 this surprisingly doesnt work ;

from django.db.models import Count
calls = Call.objects.all().order_by('-call_time')[:100]
groups = calls.values('calltype').annotate(Count('calltype'))

it works but returns on the whole objects, not only the 100 selected! cant understand.

but this workaround could help (today calls summary grouped by calltype) :

import datetime
Call.objects.order_by('-call_time').filter(call_time__gte=datetime.datetime.today() - datetime.timedelta(days=1)).values('calltype').annotate(Count('calltype'))

Answer 2

try this:

calls = Call.objects.all().order_by('-call_time')[:100]
types = CallType.objects.filter(call__in=calls).annotate(Count('call'))

you might need to add distinct() to the latter queryset though.