django-annotate

I have a Booking model that has start and end datetime fields. I want to know how many days a booking covers. I can do this in Python but I need this value for further annotations. Here's what I've tried: In [1]: Booking.objects.annotate(days=F('end')-F('start'))[0].days Out[1]: datetime.timedelta(16, 50400) There are a few problems here: I want an integer (or other number type I can use in calculations) of days as the output, not a timedelta. Setting output_field doesn't do anything meaningful here. My sums are based on date times . Subtractions like this, without removing the time could lead

Using Django I have a field which is of type JSONField. I am wanting to get a distinct count on a nested key/value in the json. With a normal field you can just do soemthing like the following model.objects.values('field_name')\ .annotate(total=Count('field_name')).order_by('-total') This does not work for a JSONField. Example Model class Pet(models.Model): data = JSONField() Example of data { 'name':'sparky', 'animal':'dog', 'diet':{ 'breakfast':'biscuits', 'dinner':'meat', } } Trying Pet.objects.values('data__diet__dinner')\ .annotate(total=Count('data__diet__dinner')).order_by('-total')

I'm trying to use django annotation to create queryset field which is a list of values of some related model attribute. queryset = ... qs = queryset.annotate( list_field=SomeAggregateFunction( Case(When(related_model__field="abc"), then="related_model__id") ), list_elements=Count(F('list_field')) ) I was thinking about about concatenating all these id with some separator, but i don't know the appropriate functions. Another solution is to make list_field a queryset . I know this syntax is wrong. Thank you for any help. If you are using postgresql and django >= 1.9 , you could use postgres

I have the following two models. class Product(models.Model): product_group=models.ForeignKey('productgroup.ProductGroup', null=False,blank=False) manufacturer=models.ForeignKey(Manufacturer, null=False,blank=False) opening_stock=models.PositiveIntegerField(default=0) class Meta: unique_together = ('product_group', 'manufacturer') and TRANSACTION_TYPE=(('I','Stock In'),('O','Stock Out')) class Stock(models.Model): product=models.ForeignKey('product.Product', blank=False,null=False) date=models.DateField(blank=False, null=False,) quantity=models.PositiveIntegerField(blank=False, null=False)

This is a bleeding-edge feature that I'm currently skewered upon and quickly bleeding out. I want to annotate a subquery-aggregate onto an existing queryset. Doing this before 1.11 either meant custom SQL or hammering the database. Here's the documentation for this , and the example from it: from django.db.models import OuterRef, Subquery, Sum comments = Comment.objects.filter(post=OuterRef('pk')).values('post') total_comments = comments.annotate(total=Sum('length')).values('total') Post.objects.filter(length__gt=Subquery(total_comments)) They're annotating on the aggregate, which seems weird