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502 lines
19 KiB
Plaintext
============================================
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Django 2.2 release notes - UNDER DEVELOPMENT
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============================================
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*Expected April 2019*
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Welcome to Django 2.2!
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These release notes cover the :ref:`new features <whats-new-2.2>`, as well as
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some :ref:`backwards incompatible changes <backwards-incompatible-2.2>` you'll
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want to be aware of when upgrading from Django 2.1 or earlier. We've
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:ref:`begun the deprecation process for some features
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<deprecated-features-2.2>`.
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See the :doc:`/howto/upgrade-version` guide if you're updating an existing
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project.
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Django 2.2 is designated as a :term:`long-term support release`. It will
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receive security updates for at least three years after its release. Support
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for the previous LTS, Django 1.11, will end in April 2020.
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Python compatibility
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====================
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Django 2.2 supports Python 3.5, 3.6, and 3.7. We **highly recommend** and only
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officially support the latest release of each series.
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.. _whats-new-2.2:
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What's new in Django 2.2
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========================
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Constraints
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-----------
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The new :class:`~django.db.models.CheckConstraint` and
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:class:`~django.db.models.UniqueConstraint` classes enable adding custom
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database constraints. Constraints are added to models using the
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:attr:`Meta.constraints <django.db.models.Options.constraints>` option.
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Minor features
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--------------
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:mod:`django.contrib.admin`
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* Added a CSS class to the column headers of
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:class:`~django.contrib.admin.TabularInline`.
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:mod:`django.contrib.auth`
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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* The ``HttpRequest`` is now passed as the first positional argument to
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:meth:`.RemoteUserBackend.configure_user`, if it accepts it.
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:mod:`django.contrib.gis`
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~~~~~~~~~~~~~~~~~~~~~~~~~
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* Added Oracle support for the
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:class:`~django.contrib.gis.db.models.functions.Envelope` function.
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* Added SpatiaLite support for the :lookup:`coveredby` and :lookup:`covers`
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lookups.
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:mod:`django.contrib.postgres`
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* The new ``ordering`` argument for
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:class:`~django.contrib.postgres.aggregates.ArrayAgg` and
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:class:`~django.contrib.postgres.aggregates.StringAgg` determines the
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ordering of the aggregated elements.
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* The new :class:`~django.contrib.postgres.indexes.BTreeIndex`,
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:class:`~django.contrib.postgres.indexes.HashIndex` and
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:class:`~django.contrib.postgres.indexes.SpGistIndex` classes allow
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creating ``B-Tree``, ``hash``, and ``SP-GiST`` indexes in the database.
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* :class:`~django.contrib.postgres.indexes.BrinIndex` now has the
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``autosummarize`` parameter.
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* The new ``search_type`` parameter of
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:class:`~django.contrib.postgres.search.SearchQuery` allows searching for
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a phrase or raw expression.
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:mod:`django.contrib.staticfiles`
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* Added path matching to the :option:`collectstatic --ignore` option so that
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patterns like ``/vendor/*.js`` can be used.
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Database backends
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~~~~~~~~~~~~~~~~~
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* Added result streaming for :meth:`.QuerySet.iterator` on SQLite.
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Generic Views
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~~~~~~~~~~~~~
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* The new :meth:`View.setup <django.views.generic.base.View.setup>` hook
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initializes view attributes before calling
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:meth:`~django.views.generic.base.View.dispatch`. It allows mixins to setup
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instance attributes for reuse in child classes.
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Internationalization
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~~~~~~~~~~~~~~~~~~~~
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* Added support and translations for the Armenian language.
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Management Commands
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~~~~~~~~~~~~~~~~~~~
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* The new :option:`--force-color` option forces colorization of the command
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output.
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* :djadmin:`inspectdb` now creates models for foreign tables on PostgreSQL.
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* :option:`inspectdb --include-views` now creates models for materialized views
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on Oracle and PostgreSQL.
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* The new :option:`inspectdb --include-partitions` option allows creating
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models for partition tables on PostgreSQL. In older versions, models are
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created child tables instead the parent.
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* :djadmin:`inspectdb` now introspects :class:`~django.db.models.DurationField`
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for Oracle and PostgreSQL, and :class:`~django.db.models.AutoField` for
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SQLite.
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* On Oracle, :djadmin:`dbshell` is wrapped with ``rlwrap``, if available.
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``rlwrap`` provides a command history and editing of keyboard input.
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* The new :option:`makemigrations --no-header` option avoids writing header
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comments in generated migration file(s). This option is also available for
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:djadmin:`squashmigrations`.
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* :djadmin:`runserver` can now use `Watchman
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<https://facebook.github.io/watchman/>`_ to improve the performance of
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watching a large number of files for changes.
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Migrations
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~~~~~~~~~~
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* The new :option:`migrate --plan` option prints the list of migration
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operations that will be performed.
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* ``NoneType`` can now be serialized in migrations.
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* You can now :ref:`register custom serializers <custom-migration-serializers>`
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for migrations.
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Models
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~~~~~~
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* Added support for PostgreSQL operator classes (:attr:`.Index.opclasses`).
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* Added support for partial indexes (:attr:`.Index.condition`).
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* Added the :class:`~django.db.models.functions.NullIf` and
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:class:`~django.db.models.functions.Reverse` database functions, as well as
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many :ref:`math database functions <math-functions>`.
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* Setting the new ``ignore_conflicts`` parameter of
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:meth:`.QuerySet.bulk_create` to ``True`` tells the database to ignore
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failure to insert rows that fail uniqueness constraints or other checks.
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* The new :class:`~django.db.models.functions.ExtractIsoYear` function extracts
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ISO-8601 week-numbering years from :class:`~django.db.models.DateField` and
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:class:`~django.db.models.DateTimeField`, and the new :lookup:`iso_year`
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lookup allows querying by an ISO-8601 week-numbering year.
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* The new :meth:`.QuerySet.bulk_update` method allows efficiently updating
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specific fields on multiple model instances.
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* Django no longer always starts a transaction when a single query is being
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performed, such as ``Model.save()``, ``QuerySet.update()``, and
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``Model.delete()``. This improves the performance of autocommit by reducing
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the number of database round trips.
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* Added SQLite support for the :class:`~django.db.models.StdDev` and
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:class:`~django.db.models.Variance` functions.
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* The handling of ``DISTINCT`` aggregation is added to the
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:class:`~django.db.models.Aggregate` class. Adding :attr:`allow_distinct =
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True <django.db.models.Aggregate.allow_distinct>` as a class attribute on
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``Aggregate`` subclasses allows a ``distinct`` keyword argument to be
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specified on initialization to ensure that the aggregate function is only
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called for each distinct value of ``expressions``.
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* The :meth:`.RelatedManager.add`, :meth:`~.RelatedManager.create`,
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:meth:`~.RelatedManager.remove`, :meth:`~.RelatedManager.set`,
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``get_or_create()``, and ``update_or_create()`` methods are now allowed on
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many-to-many relationships with intermediate models. The new
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``through_defaults`` argument is used to specify values for new intermediate
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model instance(s).
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Requests and Responses
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~~~~~~~~~~~~~~~~~~~~~~
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* Added :attr:`.HttpRequest.headers` to allow simple access to a request's
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headers.
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Serialization
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~~~~~~~~~~~~~
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* You can now deserialize data using natural keys containing :ref:`forward
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references <natural-keys-and-forward-references>` by passing
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``handle_forward_references=True`` to ``serializers.deserialize()``.
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Additionally, :djadmin:`loaddata` handles forward references automatically.
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Tests
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~~~~~
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* The new :meth:`.SimpleTestCase.assertURLEqual` assertion checks for a given
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URL, ignoring the ordering of the query string.
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:meth:`~.SimpleTestCase.assertRedirects` uses the new assertion.
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* The test :class:`~.django.test.Client` now supports automatic JSON
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serialization of list and tuple ``data`` when
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``content_type='application/json'``.
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* The new :setting:`ORACLE_MANAGED_FILES <TEST_ORACLE_MANAGED_FILES>` test
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database setting allows using Oracle Managed Files (OMF) tablespaces.
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* Deferrable database constraints are now checked at the end of each
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:class:`~django.test.TestCase` test on SQLite 3.20+, just like on other
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backends that support deferrable constraints. These checks aren't implemented
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for older versions of SQLite because they would require expensive table
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introspection there.
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* :class:`~django.test.runner.DiscoverRunner` now skips the setup of databases
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not :ref:`referenced by tests<testing-multi-db>`.
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URLs
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~~~~
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* The new :attr:`.ResolverMatch.route` attribute stores the route of the
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matching URL pattern.
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Validators
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~~~~~~~~~~
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* :class:`.MaxValueValidator`, :class:`.MinValueValidator`,
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:class:`.MinLengthValidator`, and :class:`.MaxLengthValidator` now accept
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a callable ``limit_value``.
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.. _backwards-incompatible-2.2:
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Backwards incompatible changes in 2.2
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=====================================
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Database backend API
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--------------------
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This section describes changes that may be needed in third-party database
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backends.
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* Third-party database backends must implement support for table check
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constraints or set ``DatabaseFeatures.supports_table_check_constraints`` to
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``False``.
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* Third party database backends must implement support for ignoring
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constraints or uniqueness errors while inserting or set
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``DatabaseFeatures.supports_ignore_conflicts`` to ``False``.
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* Third party database backends must implement introspection for
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``DurationField`` or set ``DatabaseFeatures.can_introspect_duration_field``
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to ``False``.
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* ``DatabaseFeatures.uses_savepoints`` now defaults to ``True``.
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* Third party database backends must implement support for partial indexes or
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set ``DatabaseFeatures.supports_partial_indexes`` to ``False``.
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* ``DatabaseIntrospection.table_name_converter()`` and
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``column_name_converter()`` are removed. Third party database backends may
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need to instead implement ``DatabaseIntrospection.identifier_converter()``.
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In that case, the constraint names that
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``DatabaseIntrospection.get_constraints()`` returns must be normalized by
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``identifier_converter()``.
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* SQL generation for indexes is moved from :class:`~django.db.models.Index` to
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``SchemaEditor`` and these ``SchemaEditor`` methods are added:
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* ``_create_primary_key_sql()`` and ``_delete_primary_key_sql()``
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* ``_delete_index_sql()`` (to pair with ``_create_index_sql()``)
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* ``_delete_unique_sql`` (to pair with ``_create_unique_sql()``)
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* ``_delete_fk_sql()`` (to pair with ``_create_fk_sql()``)
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* ``_create_check_sql()`` and ``_delete_check_sql()``
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Admin actions are no longer collected from base ``ModelAdmin`` classes
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----------------------------------------------------------------------
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For example, in older versions of Django::
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from django.contrib import admin
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class BaseAdmin(admin.ModelAdmin):
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actions = ['a']
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class SubAdmin(BaseAdmin):
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actions = ['b']
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``SubAdmin`` will have actions ``'a'`` and ``'b'``.
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Now ``actions`` follows standard Python inheritance. To get the same result as
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before::
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class SubAdmin(BaseAdmin):
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actions = BaseAdmin.actions + ['b']
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:mod:`django.contrib.gis`
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-------------------------
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* Support for GDAL 1.9 and 1.10 is dropped.
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``TransactionTestCase`` serialized data loading
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-----------------------------------------------
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Initial data migrations are now loaded in
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:class:`~django.test.TransactionTestCase` at the end of the test, after the
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database flush. In older versions, this data was loaded at the beginning of the
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test, but this prevents the :option:`test --keepdb` option from working
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properly (the database was empty at the end of the whole test suite). This
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change shouldn't have an impact on your tests unless you've customized
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:class:`~django.test.TransactionTestCase`'s internals.
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``sqlparse`` is required dependency
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-----------------------------------
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To simplify a few parts of Django's database handling, `sqlparse
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<https://pypi.org/project/sqlparse/>`_ is now a required dependency. It's
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automatically installed along with Django.
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``cached_property`` aliases
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---------------------------
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In usage like::
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from django.utils.functional import cached_property
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class A:
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@cached_property
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def base(self):
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return ...
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alias = base
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``alias`` is not cached. Such usage now raises ``TypeError: Cannot assign the
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same cached_property to two different names ('base' and 'alias').`` on Python
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3.6 and later.
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Use this instead::
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import operator
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class A:
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...
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alias = property(operator.attrgetter('base'))
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Permissions for proxy models
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----------------------------
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:ref:`Permissions for proxy models <proxy-models-permissions-topic>` are now
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created using the content type of the proxy model rather than the content type
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of the concrete model. A migration will update existing permissions when you
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run :djadmin:`migrate`.
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In the admin, the change is transparent for proxy models having the same
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``app_label`` as their concrete model. However, in older versions, users with
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permissions for a proxy model with a *different* ``app_label`` than its
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concrete model couldn't access the model in the admin. That's now fixed, but
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you might want to audit the permissions assignments for such proxy models
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(``[add|view|change|delete]_myproxy``) prior to upgrading to ensure the new
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access is appropriate.
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Finally, proxy model permission strings must be updated to use their own
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``app_label``. For example, for ``app.MyProxyModel`` inheriting from
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``other_app.ConcreteModel``, update
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``user.has_perm('other_app.add_myproxymodel')`` to
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``user.has_perm('app.add_myproxymodel')``.
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Miscellaneous
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-------------
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* To improve readability, the ``UUIDField`` form field now displays values with
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dashes, e.g. ``550e8400-e29b-41d4-a716-446655440000`` instead of
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``550e8400e29b41d4a716446655440000``.
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* On SQLite, ``PositiveIntegerField`` and ``PositiveSmallIntegerField`` now
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include a check constraint to prevent negative values in the database. If you
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have existing invalid data and run a migration that recreates a table, you'll
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see ``CHECK constraint failed``.
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* For consistency with WSGI servers, the test client now sets the
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``Content-Length`` header to a string rather than an integer.
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* The return value of :func:`django.utils.text.slugify` is no longer marked as
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HTML safe.
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* The default truncation character used by the :tfilter:`urlizetrunc`,
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:tfilter:`truncatechars`, :tfilter:`truncatechars_html`,
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:tfilter:`truncatewords`, and :tfilter:`truncatewords_html` template filters
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is now the real ellipsis character (``…``) instead of 3 dots. You may have to
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adapt some test output comparisons.
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* Support for bytestring paths in the template filesystem loader is removed.
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* :func:`django.utils.http.urlsafe_base64_encode` now returns a string instead
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of a bytestring, and :func:`django.utils.http.urlsafe_base64_decode` may no
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longer be passed a bytestring.
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* Support for ``cx_Oracle`` < 6.0 is removed.
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* The minimum supported version of ``mysqlclient`` is increased from 1.3.7 to
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1.3.13.
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* The minimum supported version of SQLite is increased from 3.7.15 to 3.8.3.
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* In an attempt to provide more semantic query data, ``NullBooleanSelect`` now
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renders ``<option>`` values of ``unknown``, ``true``, and ``false`` instead
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of ``1``, ``2``, and ``3``. For backwards compatibility, the old values are
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still accepted as data.
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* :attr:`Group.name <django.contrib.auth.models.Group.name>` ``max_length``
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is increased from 80 to 150 characters.
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* Tests that violate deferrable database constraints now error when run on
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SQLite 3.20+, just like on other backends that support such constraints.
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* To catch usage mistakes, the test :class:`~django.test.Client` and
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:func:`django.utils.http.urlencode` now raise ``TypeError`` if ``None`` is
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passed as a value to encode because ``None`` can't be encoded in GET and POST
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data. Either pass an empty string or omit the value.
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* The :djadmin:`ping_google` management command now defaults to ``https``
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instead of ``http`` for the sitemap's URL. If your site uses http, use the
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new :option:`ping_google --sitemap-uses-http` option. If you use the
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:func:`~django.contrib.sitemaps.ping_google` function, set the new
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``sitemap_uses_https`` argument to ``False``.
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* :djadmin:`runserver` no longer supports `pyinotify` (replaced by Watchman).
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* The :class:`~django.db.models.Avg`, :class:`~django.db.models.StdDev`, and
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:class:`~django.db.models.Variance` aggregate functions now return a
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``Decimal`` instead of a ``float`` when the input is ``Decimal``.
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* Tests will fail on SQLite if apps without migrations have relations to apps
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with migrations. This has been a documented restriction since migrations were
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added in Django 1.7, but it fails more reliably now. You'll see tests failing
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with errors like ``no such table: <app_label>_<model>``. This was observed
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with several third-party apps that had tests models without migrations. You
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must add migrations for such models.
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.. _deprecated-features-2.2:
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Features deprecated in 2.2
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==========================
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Model ``Meta.ordering`` will no longer affect ``GROUP BY`` queries
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------------------------------------------------------------------
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A model's ``Meta.ordering`` affecting ``GROUP BY`` queries (such as
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``.annotate().values()``) is a common source of confusion. Such queries now
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issue a deprecation warning with the advice to add an ``order_by()`` to retain
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the current query. ``Meta.ordering`` will be ignored in such queries starting
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in Django 3.1.
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Miscellaneous
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-------------
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* ``django.utils.timezone.FixedOffset`` is deprecated in favor of
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:class:`datetime.timezone`.
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* The undocumented ``QuerySetPaginator`` alias of
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``django.core.paginator.Paginator`` is deprecated.
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* The ``FloatRangeField`` model and form fields in ``django.contrib.postgres``
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are deprecated in favor of a new name, ``DecimalRangeField``, to match the
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underlying ``numrange`` data type used in the database.
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* The ``FILE_CHARSET`` setting is deprecated. Starting with Django 3.1, files
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read from disk must be UTF-8 encoded.
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* ``django.contrib.staticfiles.storage.CachedStaticFilesStorage`` is
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deprecated due to the intractable problems that is has. Use
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:class:`.ManifestStaticFilesStorage` or a third-party cloud storage instead.
|
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* :meth:`.RemoteUserBackend.configure_user` is now passed ``request`` as the
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first positional argument, if it accepts it. Support for overrides that don't
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accept it will be removed in Django 3.1.
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* The :attr:`.SimpleTestCase.allow_database_queries`,
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:attr:`.TransactionTestCase.multi_db`, and :attr:`.TestCase.multi_db`
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attributes are deprecated in favor of :attr:`.SimpleTestCase.databases`,
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:attr:`.TransactionTestCase.databases`, and :attr:`.TestCase.databases`.
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These new attributes allow databases dependencies to be declared in order to
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prevent unexpected queries against non-default databases to leak state
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between tests. The previous behavior of ``allow_database_queries=True`` and
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``multi_db=True`` can be achieved by setting ``databases='__all__'``.
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