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
We can perform a GROUP BY … COUNT or a GROUP BY … SUM SQL equivalent queries on Django ORM, with the use of annotate(), values(), the django.db.models‘s Count and Sum methods respectfully and optionally the order_by() method: GROUP BY … COUNT: from django.db.models import Count result = Books.objects.values(‘author’) .order_by(‘author’) .annotate(count=Count(‘author’)) Now result contains a … Read more
This is dangerously close to being non-constructive, but I’ll bite. Suppose we need to maintain inventories of certain items for a number of different, let’s say, accounts. DDL follows: CREATE TABLE account ( id serial PRIMARY KEY, … ); CREATE TABLE item ( id serial PRIMARY KEY, name text NOT NULL, … ); CREATE TABLE … Read more
Use __contains or __icontains (case-insensitive): result = table.objects.filter(string__contains=”pattern”) The SQL equivalent is SELECT … WHERE string LIKE ‘%pattern%’; @Dmitri’s answer below covers patterns like ‘pattern%’ or ‘%pattern’
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 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).
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
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
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