I've created a custom Manager for a Django model which returns a QuerySet holding a subset of objects.all(). I need this to be the model's default Manager, since I am also creating a custom tag which will retrieve content from any model (specified by an argument), and needs to use the default Manager for the specified model. All that works fine, except - Django Admin is ALSO using the default Manager for this particular model, which means that not all model instances appear in the admin.
The Django docs don't help:
If you use custom Manager objects, take note that the first Manager Django encounters (in the order in which they're defined in the model) has a special status. Django interprets this first Manager defined in a class as the "default" Manager, and several parts of Django (though not the admin application) will use that Manager exclusively for that model. (Django Managers documentation)
The admin isn't supposed to use the default Manager, but it seems to be in my case. Note that I have also explicitly add the default Manager objects
:
subset = CustomManager() # the default manager objects = models.Manager() # the one I want admin to use
How can I specify which Manager the admin should use?
You can use a custom Manager in a particular model by extending the base Manager class and instantiating your custom Manager in your model. There are two reasons you might want to customize a Manager : to add extra Manager methods, and/or to modify the initial QuerySet the Manager returns.
The default Manager object that Django provides in models is “objects“. Here “objects” is the manager object that Django creates by default. The 'create' method creates a new object. It takes field values that the model class wants.
Django, by default, uses SQLite3 for development. SQLite3 is a simple relational database engine and your database is automatically created as db. sqlite3 the first time you run python manage.py migrate .
You can choose the manager by overriding the queryset
method in your ModelAdmin subclass.
def get_queryset(self, request): # use our manager, rather than the default one qs = self.model.objects.get_queryset() # we need this from the superclass method ordering = self.ordering or () # otherwise we might try to *None, which is bad ;) if ordering: qs = qs.order_by(*ordering) return qs
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