You can just do: try: obj = Model.objects.get(**kwargs) except Model.DoesNotExist: obj = Model(**dict((k,v) for (k,v) in kwargs.items() if ‘__’ not in k)) which is pretty much what get_or_create does, sans commit.
There is no difference, the second one implies using the __exact. From the documentation: For example, the following two statements are equivalent: >>> Blog.objects.get(id__exact=14) # Explicit form >>> Blog.objects.get(id=14) # __exact is implied This is for convenience, because exact # lookups are the common case.
Update: Since Django 2.1, everything works out of the box. No workarounds needed and the produced query is correct. This is maybe a bit too late, but I have found the solution (tested with Django 1.11.1). The problem is, call to .values(‘publisher’), which is required to provide grouping, removes all annotations, that are not included … Read more
You can create a custom manager, and simply override get_queryset for it to apply everywhere. For example: class MyManager(models.Manager): def get_queryset(self): return super(MyManager, self).get_queryset().select_related(‘foo’, ‘bar’) (Prior to Django 1.6, it was get_query_set).
I had a similar requirement although not for RESTful purposes. I was able to achieve what I needed by using a “full” serializing module, in my case Django Full Serializers. This is part of wadofstuff and is distributed under the new BSD license. Wadofstuff makes this quite easy. For e.g. in your case you’d need … Read more
For those who are still looking for an efficient way to bulk delete in django, here’s a possible solution: The reason delete() may be so slow is twofold: 1) Django has to ensure cascade deleting functions properly, thus looking for foreign key references to your models; 2) Django has to handle pre and post-save signals … Read more
you can try this class Foo(admin.ModelAdmin): list_select_related = ( ‘foreign_key1’, ‘foreign_key2’, ) https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_select_related
If you want to retrieve Book instances and prefetch the related tags use Book.objects.prefetch_related(‘tags’). No need to use the reverse relation here. You can also have a look at the related tests in the Django source code. Also the Django documentation states that prefetch_related() is supposed to work with GenericForeignKey and GenericRelation: prefetch_related, on the … Read more
You can do this by following the backwards relation in the lookup. >>> qs = Department.objects.filter( … departmentvolunteer__isnull=True).values_list(‘name’, flat=True) >>> print(qs.query) SELECT “app_department”.”name” FROM “app_department” LEFT OUTER JOIN “app_departmentvolunteer” ON ( “app_department”.”id” = “app_departmentvolunteer”.”department_id” ) WHERE “app_departmentvolunteer”.”id” IS NULL Here are the docs on queries “Spanning multi-valued relationships”: https://docs.djangoproject.com/en/stable/topics/db/queries/#spanning-multi-valued-relationships
You are actually asking two different questions: 1. does using select_related actually creates performance overhead? You should see documentation about Django Query Cache: Understand QuerySet evaluation To avoid performance problems, it is important to understand: that QuerySets are lazy. when they are evaluated. how the data is held in memory. So in summary, Django caches … Read more