Django ORM - objects.filter() vs. objects.all().filter() - which one is preferred?

Question

Very often I see constructs like ``` MyModel.objects.all().filter(...) ``` which will return a QuerySet of the default Mananger. At first `all()` seems to be quite redundant, because ``` MyMode.objects.filter(...) ``` delivers the same result. However, this seems to be safe for the default Manager only, because of the following two statements in the Django documentation: Excerpt from the Chapter "Adding extra manager methods" A custom Manager method can return anything you want. It doesn’t have to return a QuerySet. Definition of the `all()` manager method: all() Returns a copy of the current QuerySet (or QuerySet subclass). This can be useful in situations where you might want to pass in either a model manager or a QuerySet and do further filtering on the result. After calling all() on either object, you’ll definitely have a QuerySet to work with. This seems a bit like a contradiction to me. On one hand Django offers the freedom to let a manager method return whatever object type is…

Accepted Answer

The method `all()` on a manager just delegates to `get_queryset()`, as you can see in the Django source code:

```
def all(self):
    return self.get_queryset()
```

So it's just a way to get the QuerySet from the Manager. This can be handy to ensure that you're dealing with a QuerySet and not a Manager, because `MyModel.objects` returns a Manager.

For example, if you want to iterate over all the items, you can't do this:

```
for item in MyModel.objects:
    # this won't work
```

Because you can't iterate over a Manager. However, `all()` returns the QuerySet, you can iterate over a QuerySet:

```
for item in MyModel.objects.all():
    # do someting with item
```

Generally, you should never overwrite `all()`. You can overwrite `get_queryset()` but this method must return a QuerySet.

If you would use a filter method like `filter()` or `exclude()`, you would already have the QuerySet, because these methods are proxied to the QuerySet. So you don't have to do something like `all().filter()`.

Django ORM - objects.filter() vs. objects.all().filter() - which one is preferred?

Solution

Problem