[Fixed]-Django objects.all() vs objects.filter()

From Django’s source code below, it is almost the same. Both methods call the _chain method. With filter, you create a Q object without any children, but the overhead is not much.

Using all is nonetheless preferable as it is avoiding unnecessary code to be executed.

def all(self):
    """
    Return a new QuerySet that is a copy of the current one. This allows a
    QuerySet to proxy for a model manager in some cases.
    """
    return self._chain()

def filter(self, *args, **kwargs):
    """
    Return a new QuerySet instance with the args ANDed to the existing
    set.
    """
    return self._filter_or_exclude(False, *args, **kwargs)

def _filter_or_exclude(self, negate, *args, **kwargs):
    if args or kwargs:
        assert self.query.can_filter(), \
            "Cannot filter a query once a slice has been taken."

    clone = self._chain()
    if negate:
        clone.query.add_q(~Q(*args, **kwargs))
    else:
        clone.query.add_q(Q(*args, **kwargs))
    return clone