============================================
Django 1.5 release notes - UNDER DEVELOPMENT
============================================

These release notes cover the `new features`_, as well
as some `backwards incompatible changes`_ you'll want to be aware of
when upgrading from Django 1.4 or older versions. We've also dropped some
features, which are detailed in :doc:`our deprecation plan
</internals/deprecation>`, and we've `begun the deprecation process for some
features`_.

.. _`new features`: `What's new in Django 1.5`_
.. _`backwards incompatible changes`: `Backwards incompatible changes in 1.5`_
.. _`begun the deprecation process for some features`: `Features deprecated in 1.5`_

Python compatibility
====================

Django 1.5 has dropped support for Python 2.5. Python 2.6 is now the minimum
required Python version. Django is tested and supported on Python 2.6 and
2.7.

This change should affect only a small number of Django users, as most
operating-system vendors today are shipping Python 2.6 or newer as their default
version. If you're still using Python 2.5, however, you'll need to stick to
Django 1.4 until you can upgrade your Python version. Per :doc:`our support policy
</internals/release-process>`, Django 1.4 will continue to receive security
support until the release of Django 1.6.

Django 1.5 does not run on Jython, because Jython doesn't currently offer any
version compatible with Python 2.6.

What's new in Django 1.5
========================

Support for saving a subset of model's fields
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The method :meth:`Model.save() <django.db.models.Model.save()>` has a new
keyword argument ``update_fields``. By using this argument it is possible to
save only a select list of model's fields. This can be useful for performance
reasons or when trying to avoid overwriting concurrent changes.

See the :meth:`Model.save() <django.db.models.Model.save()>` documentation for
more details.

Caching of related model instances
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When traversing relations, the ORM will avoid re-fetching objects that were
previously loaded. For example, with the tutorial's models::

    >>> first_poll = Poll.objects.all()[0]
    >>> first_choice = first_poll.choice_set.all()[0]
    >>> first_choice.poll is first_poll
    True

In Django 1.5, the third line no longer triggers a new SQL query to fetch
``first_choice.poll``; it was set when by the second line.

For one-to-one relationships, both sides can be cached. For many-to-one
relationships, only the single side of the relationship can be cached. This
is particularly helpful in combination with ``prefetch_related``.

Minor features
~~~~~~~~~~~~~~

Django 1.5 also includes several smaller improvements worth noting:

* The template engine now interprets ``True``, ``False`` and ``None`` as the
  corresponding Python objects.

* :mod:`django.utils.timezone` provides a helper for converting aware
  datetimes between time zones. See :func:`~django.utils.timezone.localtime`.

* The generic views support OPTIONS requests.

* In the localflavor for Canada, "pq" was added to the acceptable codes for
  Quebec. It's an old abbreviation.

Backwards incompatible changes in 1.5
=====================================

.. warning::

    In addition to the changes outlined in this section, be sure to review the
    :doc:`deprecation plan </internals/deprecation>` for any features that
    have been removed. If you haven't updated your code within the
    deprecation timeline for a given feature, its removal may appear as a
    backwards incompatible change.

Context in year archive class-based views
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For consistency with the other date-based generic views,
:class:`~django.views.generic.dates.YearArchiveView` now passes ``year`` in
the context as a :class:`datetime.date` rather than a string.  If you are
using ``{{ year }}`` in your templates, you must replace it with ``{{
year|date:"Y" }}``.

``next_year`` and ``previous_year`` were also added in the context. They are
calculated according to ``allow_empty`` and ``allow_future``.

Features deprecated in 1.5
==========================

``django.utils.simplejson``
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Since Django 1.5 drops support for Python 2.5, we can now rely on the
:mod:`json` module being in Python's standard library -- so we've removed
our own copy of ``simplejson``. You can safely change any use of
:mod:`django.utils.simplejson` to :mod:`json`.

``itercompat.product``
~~~~~~~~~~~~~~~~~~~~~~

The :func:`~django.utils.itercompat.product` function has been deprecated. Use
the built-in :func:`itertools.product` instead.