update() is converted directly to an SQL statement; it doesn’t call save() on the model instances, and so the pre_save and post_save signals aren’t emitted. If you want your signal receivers to be called, you should loop over the queryset, and for each model instance, make your changes and call save() yourself.
Try this: block in group.block_set.all()
You may not be able to do it directly. From the documentation of list_display ManyToManyField fields aren’t supported, because that would entail executing a separate SQL statement for each row in the table. If you want to do this nonetheless, give your model a custom method, and add that method’s name to list_display. (See below … Read more
I would focus on the example queries rather than your quote from the documentation. Aggregate calculates values for the entire queryset. Annotate calculates summary values for each item in the queryset. Aggregation >>> Book.objects.aggregate(average_price=Avg(‘price’)) {‘average_price’: 34.35} Returns a dictionary containing the average price of all books in the queryset. Annotation >>> q = Book.objects.annotate(num_authors=Count(‘authors’)) >>> … Read more
Greater than: Person.objects.filter(age__gt=20) Greater than or equal to: Person.objects.filter(age__gte=20) Less than: Person.objects.filter(age__lt=20) Less than or equal to: Person.objects.filter(age__lte=20) You can find them all in [the documentation].(https://docs.djangoproject.com/en/stable/ref/models/querysets/).
Concatenating the querysets into a list is the simplest approach. If the database will be hit for all querysets anyway (e.g. because the result needs to be sorted), this won’t add further cost. from itertools import chain result_list = list(chain(page_list, article_list, post_list)) Using itertools.chain is faster than looping each list and appending elements one by … Read more
Project.objects.values(‘client’).distinct() Link to Django docs on queryset distinct() method
Two querysets are documented way of doing this. It will be one database hit anyway. test_ids = Subject.objects.all() result = Test.objects.filter(test_id__in=test_ids).filter([some other filtering])
Here is the code: class PassengerList(generics.ListCreateAPIView): model = Passenger serializer_class = PassengerSerializer # Show all of the PASSENGERS in particular WORKSPACE # or all of the PASSENGERS in particular AIRLINE def get_queryset(self): queryset = Passenger.objects.all() workspace = self.request.query_params.get(‘workspace’) airline = self.request.query_params.get(‘airline’) if workspace: queryset = queryset.filter(workspace_id=workspace) elif airline: queryset = queryset.filter(workspace__airline_id=airline) return queryset
Both are lazily evaluated, so I would expect them to perform equivalently. The SQL is likely different, but with no real distinction.