Fixed doc references to `django.db.models.query.QuerySet` and converted some...

A shortcut: get_object_or_404()

-------------------------------

It's a very common idiom to use :meth:`~django.db.models.QuerySet.get` and raise

:exc:`~django.http.Http404` if the object doesn't exist. Django provides a

shortcut. Here's the ``detail()`` view, rewritten::

It's a very common idiom to use :meth:`~django.db.models.query.QuerySet.get`

and raise :exc:`~django.http.Http404` if the object doesn't exist. Django

provides a shortcut. Here's the ``detail()`` view, rewritten::

    from django.shortcuts import render_to_response, get_object_or_404

    # ...

The :func:`~django.shortcuts.get_object_or_404` function takes a Django model

as its first argument and an arbitrary number of keyword arguments, which it

passes to the module's :meth:`~django.db.models.QuerySet.get` function. It

raises :exc:`~django.http.Http404` if the object doesn't exist.

passes to the module's :meth:`~django.db.models.query.QuerySet.get` function.

It raises :exc:`~django.http.Http404` if the object doesn't exist.

.. admonition:: Philosophy

There's also a :func:`~django.shortcuts.get_list_or_404` function, which works

just as :func:`~django.shortcuts.get_object_or_404` -- except using

:meth:`~django.db.models.QuerySet.filter` instead of

:meth:`~django.db.models.QuerySet.get`. It raises :exc:`~django.http.Http404` if

the list is empty.

:meth:`~django.db.models.query.QuerySet.filter` instead of

:meth:`~django.db.models.query.QuerySet.get`. It raises

:exc:`~django.http.Http404` if the list is empty.

Write a 404 (page not found) view

=================================

    that operate upon a list of object instances. Requires that the view it is

    mixed with provides ``self.object_list``, the list of object instances that

    the view is operating on. ``self.object_list`` may be, but is not required

    to be, a :class:`~django.db.models.Queryset`.

    to be, a :class:`~django.db.models.query.QuerySet`.

    **Extends**

        Returns the list of dates of type ``date_type`` for which

        ``queryset`` contains entries. For example, ``get_date_list(qs,

        'year')`` will return the list of years for which ``qs`` has entries.

        See :meth:`~django.db.models.QuerySet.dates()` for the

        See :meth:`~django.db.models.query.QuerySet.dates()` for the

        ways that the ``date_type`` argument can be used.

.. warning::

    The "delete selected objects" action uses :meth:`QuerySet.delete()

    <django.db.models.QuerySet.delete>` for efficiency reasons, which has an

    important caveat: your model's ``delete()`` method will not be called.

    <django.db.models.query.QuerySet.delete>` for efficiency reasons, which

    has an important caveat: your model's ``delete()`` method will not be

    called.

    If you wish to override this behavior, simply write a custom action which

    accomplishes deletion in your preferred manner -- for example, by calling

    * The current :class:`ModelAdmin`

    * An :class:`~django.http.HttpRequest` representing the current request,

    * A :class:`~django.db.models.QuerySet` containing the set of objects

      selected by the user.

    * A :class:`~django.db.models.query.QuerySet` containing the set of

      objects selected by the user.

Our publish-these-articles function won't need the :class:`ModelAdmin` or the

request object, but we will use the queryset::

.. attribute:: ModelAdmin.list_select_related

    Set ``list_select_related`` to tell Django to use

    :meth:`~django.db.models.QuerySet.select_related` in retrieving the list of

    objects on the admin change list page. This can save you a bunch of

    database queries.

    :meth:`~django.db.models.query.QuerySet.select_related` in retrieving

    the list of objects on the admin change list page. This can save you a

    bunch of database queries.

    The value should be either ``True`` or ``False``. Default is ``False``.

    Note that Django will use :meth:`~django.db.models.QuerySet.select_related`,

    Note that Django will use

    :meth:`~django.db.models.query.QuerySet.select_related`,

    regardless of this setting if one of the ``list_display`` fields is a

    ``ForeignKey``.

.. method:: ModelAdmin.queryset(self, request)

    The ``queryset`` method on a ``ModelAdmin`` returns a

    :class:`~django.db.models.QuerySet` of all model instances that can be

    edited by the admin site. One use case for overriding this method is

    to show objects owned by the logged-in user::

    :class:`~django.db.models.query.QuerySet` of all model instances that

    can be edited by the admin site. One use case for overriding this method

    is to show objects owned by the logged-in user::

        class MyModelAdmin(admin.ModelAdmin):

            def queryset(self, request):

    Takes a set of valid :ref:`lookup arguments <field-lookups-intro>` for the

    model the :class:`~django.contrib.contenttypes.models.ContentType`

    represents, and does :meth:`a get() lookup <django.db.models.QuerySet.get>`

    represents, and does

    :meth:`a get() lookup <django.db.models.query.QuerySet.get>`

    on that model, returning the corresponding object.

.. method:: ContentType.model_class()

This will not work correctly, however. The generic relation adds extra filters

to the queryset to ensure the correct content type, but the

:meth:`~django.db.models.QuerySet.aggregate` method doesn't take them into

account. For now, if you need aggregates on generic relations, you'll need

to calculate them without using the aggregation API.

:meth:`~django.db.models.query.QuerySet.aggregate` method doesn't take them

into account. For now, if you need aggregates on generic relations, you'll

need to calculate them without using the aggregation API.

Generic relations in forms and admin

------------------------------------