django-queryset

I am using Django to develop a course registration site for an educational institution. Suppose I have two Django query sets, one that comprises of courses that occupy session 1 (set A) and one that comprises of courses in session 2 (set B): A = session1.courses.all() B = session2.courses.all() There is much overlap between these two query sets. What is an efficient way to obtain the set of courses within set B, but not in set A? I believe this is equivalent to taking out the intersection of the two sets from set B. Thank you! A.exclude(pk__in = B) should work Starting from version 1.11 ,

I have a Django form setup using GET method. Each value corresponds to attributes of a Django model. What would be the most elegant way to generate the query? Currently this is what I do in the view: def search_items(request): if 'search_name' in request.GET: query_attributes = {} query_attributes['color'] = request.GET.get('color', '') if not query_attributes['color']: del query_attributes['color'] query_attributes['shape'] = request.GET.get('shape', '') if not query_attributes['shape']: del query_attributes['shape'] items = Items.objects.filter(**query_attributes) But I'm pretty sure there's

i got a problem with an Django application. Queries on the model Scope are extremly slow and after some debugging i still got no clue where the problem is. When i query the db like scope = Scope.objects.get(pk='Esoterik I') in django it takes 5 to 10 seconds. The database has less than 10 entries and an index on the primary key. so it is way too slow. When executing the an equivalent query on the db like SELECT * FROM scope WHERE title='Esoterik I'; everything is ok, it takes only about 50ms. Same problem happens if i do a query with a set of results like scope_list = Scope.objects.filter

I'm trying to find the cumulated duration of some events, 'start' and 'end' field are both django.db.models.DateTimeField fields. What I would like to do should have been written like this: from django.db.models import F, Sum from my.models import Event Event.objects.aggregate(anything=Sum(F('start') - F('end'))) # this first example return: # AttributeError: 'ExpressionNode' object has no attribute 'split' # Ok I'll try more SQLish: Event.objects.extra(select={ 'extra_field': 'start - end' }).aggregate(Sum('extra_field')) # this time: # FieldError: Cannot resolve keyword 'extra_field' into

So here's what I'm trying to do. I've a list with years inside, for instance years = [2002, 2003, 2004] and I've a SomethingModel with a DateField I want to do a query that will return me all the objects that belongs to that year: I known this work: SomethingModel.objects.filter(date__year=2003) SomethingModel.objects.filter(date__in=[list with dates]) So I've tried this: SomethingModel.objects.filter(date__year__in=years) but this return me this error: FieldError: Join on field 'date' not permitted. Did you misspell 'year' for the lookup type? Does anyone has any idea how to do this? In a

While constructing a complexe QuerySet with several annotations, I ran into an issue that I could reproduce with the following simple setup. Here are the models: class Player(models.Model): name = models.CharField(max_length=200) class Unit(models.Model): player = models.ForeignKey(Player, on_delete=models.CASCADE, related_name='unit_set') rarity = models.IntegerField() class Weapon(models.Model): unit = models.ForeignKey(Unit, on_delete=models.CASCADE, related_name='weapon_set') With my test database, I obtain the following (correct) results: Player.objects.annotate(weapon_count=Count('unit

Is there a way in Django to write a query using the ORM, not raw SQL that allows you to JOIN on another table without there being a foreign key? Looking through the documentation it appears in order for the One to One relationship to work there must be a foreign key present? In the models below I want to run a query with a JOIN on UserActivity.request_url to UserActivityLink.url. class UserActivity(models.Model): id = models.IntegerField(primary_key=True) last_activity_ip = models.CharField(max_length=45L, blank=True) last_activity_browser = models.CharField(max_length=255L, blank=True) last