[1.7.x] Fixed #24613 -- Added example to QuerySet.defer() documentation

    reader, is slightly faster and consumes a little less memory in the Python

    process.

    For example, both of these models use the same underlying database table::

        class CommonlyUsedModel(models.Model):

            f1 = models.CharField(max_length=10)

            class Meta:

                managed = False

                db_table = 'app_largetable'

        class ManagedModel(models.Model):

            f1 = models.CharField(max_length=10)

            f2 = models.CharField(max_length=10)

            class Meta:

                db_table = 'app_largetable'

        # Two equivalent QuerySets:

        CommonlyUsedModel.objects.all()

        ManagedModel.objects.all().defer('f2')

    If many fields need to be duplicated in the unmanaged model, it may be best

    to create an abstract model with the shared fields and then have the

    unmanaged and managed models inherit from the abstract model.

.. note::

    When calling :meth:`~django.db.models.Model.save()` for instances with