# Τεκμηρίωση του Django - 5.2.8

# Django 4.2 release notes

April 3, 2023

Welcome to Django 4.2!

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 4.1 or earlier. We’ve begun the deprecation process for some features.

See the How to upgrade Django to a newer version guide if you’re updating an existing project.

Django 4.2 is designated as a long-term support release. It will receive security updates for at least three years after its release. Support for the previous LTS, Django 3.2, will end in April 2024.

## Python compatibility

Django 4.2 supports Python 3.8, 3.9, 3.10, 3.11, and 3.12 (as of 4.2.8). We highly recommend and only officially support the latest release of each series.

## What’s new in Django 4.2

### Psycopg 3 support

Django now supports psycopg version 3.1.8 or higher. To update your code, install the psycopg library, you don’t need to change the `ENGINE` as `django.db.backends.postgresql` supports both libraries.

Support for `psycopg2` is likely to be deprecated and removed at some point in the future.

Be aware that `psycopg` 3 introduces some breaking changes over `psycopg2`. As a consequence, you may need to make some changes to account for differences from psycopg2.

### Comments on columns and tables

The new `Field.db_comment` and `Meta.db_table_comment` options allow creating comments on columns and tables, respectively. For example:

    from django.db import models

    class Question(models.Model):
        text = models.TextField(db_comment="Poll question")
        pub_date = models.DateTimeField(
            db_comment="Date and time when the question was published",
        )

        class Meta:
            db_table_comment = "Poll questions"

    class Answer(models.Model):
        question = models.ForeignKey(
            Question,
            on_delete=models.CASCADE,
            db_comment="Reference to a question",
        )
        answer = models.TextField(db_comment="Question answer")

        class Meta:
            db_table_comment = "Question answers"

Also, the new `AlterModelTableComment` operation allows changing table comments defined in the `Meta.db_table_comment`.

### Mitigation for the BREACH attack

`GZipMiddleware` now includes a mitigation for the BREACH attack. It will add up to 100 random bytes to gzip responses to make BREACH attacks harder. Read more about the mitigation technique in the Heal The Breach (HTB) paper.

### In-memory file storage

The new `django.core.files.storage.InMemoryStorage` class provides a non-persistent storage useful for speeding up tests by avoiding disk access.

### Custom file storages

The new `STORAGES` setting allows configuring multiple custom file storage backends. It also controls storage engines for managing files (the `"default"` key) and static files (the `"staticfiles"` key).

The old `DEFAULT_FILE_STORAGE` and `STATICFILES_STORAGE` settings are deprecated as of this release.

### Minor features

#### `django.contrib.admin`

- The light or dark color theme of the admin can now be toggled in the UI, as well as being set to follow the system setting.

- The admin’s font stack now prefers system UI fonts and no longer requires downloading fonts. Additionally, CSS variables are available to more easily override the default font families.

- The admin/delete_confirmation.html template now has some additional blocks and scripting hooks to ease customization.

- The chosen options of `filter_horizontal` and `filter_vertical` widgets are now filterable.

- The `admin/base.html` template now has a new block `nav-breadcrumbs` which contains the navigation landmark and the `breadcrumbs` block.

- `ModelAdmin.list_editable` now uses atomic transactions when making edits.

- jQuery is upgraded from version 3.6.0 to 3.6.4.

#### `django.contrib.auth`

- The default iteration count for the PBKDF2 password hasher is increased from 390,000 to 600,000.

- `UserCreationForm` now saves many-to-many form fields for a custom user model.

- The new `BaseUserCreationForm` is now the recommended base class for customizing the user creation form.

#### `django.contrib.gis`

- The GeoJSON serializer now outputs the `id` key for serialized features, which defaults to the primary key of objects.

- The `GDALRaster` class now supports `pathlib.Path`.

- The `GeoIP2` class now supports `.mmdb` files downloaded from DB-IP.

- The OpenLayers template widget no longer includes inline CSS (which also removes the former `map_css` block) to better comply with a strict Content Security Policy.

- `OpenLayersWidget` is now based on OpenLayers 7.2.2 (previously 4.6.5).

- The new `isempty` lookup and `IsEmpty()` expression allow filtering empty geometries on PostGIS.

- The new `FromWKB()` and `FromWKT()` functions allow creating geometries from Well-known binary (WKB) and Well-known text (WKT) representations.

#### `django.contrib.postgres`

- The new `trigram_strict_word_similar` lookup, and the `TrigramStrictWordSimilarity()` and `TrigramStrictWordDistance()` expressions allow using trigram strict word similarity.

- The `arrayfield.overlap` lookup now supports `QuerySet.values()` and `values_list()` as a right-hand side.

#### `django.contrib.sitemaps`

- The new `Sitemap.get_languages_for_item()` method allows customizing the list of languages for which the item is displayed.

#### `django.contrib.staticfiles`

- `ManifestStaticFilesStorage` now has experimental support for replacing paths to JavaScript modules in `import` and `export` statements with their hashed counterparts. If you want to try it, subclass `ManifestStaticFilesStorage` and set the `support_js_module_import_aggregation` attribute to `True`.

- The new `ManifestStaticFilesStorage.manifest_hash` attribute provides a hash over all files in the manifest and changes whenever one of the files changes.

#### Database backends

- The new `"assume_role"` option is now supported in `OPTIONS` on PostgreSQL to allow specifying the session role.

- The new `"server_side_binding"` option is now supported in `OPTIONS` on PostgreSQL with `psycopg` 3.1.8+ to allow using server-side binding cursors.

#### Error Reporting

- The debug page now shows exception notes and fine-grained error locations on Python 3.11+.

- Session cookies are now treated as credentials and therefore hidden and replaced with stars (`**********`) in error reports.

#### Forms

- `ModelForm` now accepts the new `Meta` option `formfield_callback` to customize form fields.

- `modelform_factory()` now respects the `formfield_callback` attribute of the `form`’s `Meta`.

#### Internationalization

- Added support and translations for the Central Kurdish (Sorani) language.

#### Logging

- The django.db.backends logger now logs transaction management queries (`BEGIN`, `COMMIT`, and `ROLLBACK`) at the `DEBUG` level.

#### Management Commands

- `makemessages` command now supports locales with private sub-tags such as `nl_NL-x-informal`.

- The new `makemigrations --update` option merges model changes into the latest migration and optimizes the resulting operations.

#### Migrations

- Migrations now support serialization of `enum.Flag` objects.

#### Models

- `QuerySet` now extensively supports filtering against Window functions with the exception of disjunctive filter lookups against window functions when performing aggregation.

- `prefetch_related()` now supports `Prefetch` objects with sliced querysets.

- Registering lookups on `Field` instances is now supported.

- The new `robust` argument for `on_commit()` allows performing actions that can fail after a database transaction is successfully committed.

- The new `KT()` expression represents the text value of a key, index, or path transform of `JSONField`.

- `Now` now supports microsecond precision on MySQL and millisecond precision on SQLite.

- `F()` expressions that output `BooleanField` can now be negated using `~F()` (inversion operator).

- `Model` now provides asynchronous versions of some methods that use the database, using an `a` prefix: `adelete()`, `arefresh_from_db()`, and `asave()`.

- Related managers now provide asynchronous versions of methods that change a set of related objects, using an `a` prefix: `aadd()`, `aclear()`, `aremove()`, and `aset()`.

- `CharField.max_length` is no longer required to be set on PostgreSQL, which supports unlimited `VARCHAR` columns.

#### Requests and Responses

- `StreamingHttpResponse` now supports async iterators when Django is served via ASGI.

#### Tests

- The `test --debug-sql` option now formats SQL queries with `sqlparse`.

- The `RequestFactory`, `AsyncRequestFactory`, `Client`, and `AsyncClient` classes now support the `headers` parameter, which accepts a dictionary of header names and values. This allows a more natural syntax for declaring headers.

      # Before:
      self.client.get("/home/", HTTP_ACCEPT_LANGUAGE="fr")
      await self.async_client.get("/home/", ACCEPT_LANGUAGE="fr")

      # After:
      self.client.get("/home/", headers={"accept-language": "fr"})
      await self.async_client.get("/home/", headers={"accept-language": "fr"})

#### Utilities

- The new `encoder` parameter for `django.utils.html.json_script()` function allows customizing a JSON encoder class.

- The private internal vendored copy of `urllib.parse.urlsplit()` now strips `'\r'`, `'\n'`, and `'\t'` (see CVE 2022-0391 and bpo-43882). This is to protect projects that may be incorrectly using the internal `url_has_allowed_host_and_scheme()` function, instead of using one of the documented functions for handling URL redirects. The Django functions were not affected.

- The new `django.utils.http.content_disposition_header()` function returns a `Content-Disposition` HTTP header value as specified by RFC 6266.

#### Validators

- The list of common passwords used by `CommonPasswordValidator` is updated to the most recent version.

## Backwards incompatible changes in 4.2

### Database backend API

This section describes changes that may be needed in third-party database backends.

- `DatabaseFeatures.allows_group_by_pk` is removed as it only remained to accommodate a MySQL extension that has been supplanted by proper functional dependency detection in MySQL 5.7.15. Note that `DatabaseFeatures.allows_group_by_selected_pks` is still supported and should be enabled if your backend supports functional dependency detection in `GROUP BY` clauses as specified by the `SQL:1999` standard.

- `inspectdb` now uses `display_size` from `DatabaseIntrospection.get_table_description()` rather than `internal_size` for `CharField`.

### Dropped support for MariaDB 10.3

Upstream support for MariaDB 10.3 ends in May 2023. Django 4.2 supports MariaDB 10.4 and higher.

### Dropped support for MySQL 5.7

Upstream support for MySQL 5.7 ends in October 2023. Django 4.2 supports MySQL 8 and higher.

### Dropped support for PostgreSQL 11

Upstream support for PostgreSQL 11 ends in November 2023. Django 4.2 supports PostgreSQL 12 and higher.

### Setting `update_fields` in `Model.save()` may now be required

In order to avoid updating unnecessary columns, `QuerySet.update_or_create()` now passes `update_fields` to the `Model.save()` calls. As a consequence, any fields modified in the custom `save()` methods should be added to the `update_fields` keyword argument before calling `super()`. See Overriding predefined model methods for more details.

### Dropped support for raw aggregations on MySQL

MySQL 8+ allows functional dependencies on `GROUP BY` columns, so the pre-Django 4.2 workaround of grouping by primary keys of the main table is removed. As a consequence, using `RawSQL()` aggregations is no longer supported on MySQL as there is no way to determine if such aggregations are needed or valid in the `GROUP BY` clause. Use Aggregation functions instead.

### Miscellaneous

- The undocumented `django.http.multipartparser.parse_header()` function is removed. Use `django.utils.http.parse_header_parameters()` instead.

- `{% blocktranslate asvar … %}` result is now marked as safe for (HTML) output purposes.

- The `autofocus` HTML attribute in the admin search box is removed as it can be confusing for screen readers.

- The `makemigrations --check` option no longer creates missing migration files.

- The `alias` argument for `Expression.get_group_by_cols()` is removed.

- The minimum supported version of `sqlparse` is increased from 0.2.2 to 0.3.1.

- The undocumented `negated` parameter of the `Exists` expression is removed.

- The `is_summary` argument of the undocumented `Query.add_annotation()` method is removed.

- The minimum supported version of SQLite is increased from 3.9.0 to 3.21.0.

- The minimum supported version of `asgiref` is increased from 3.5.2 to 3.6.0.

- `UserCreationForm` now rejects usernames that differ only in case. If you need the previous behavior, use `BaseUserCreationForm` instead.

- The minimum supported version of `mysqlclient` is increased from 1.4.0 to 1.4.3.

- The minimum supported version of `argon2-cffi` is increased from 19.1.0 to 19.2.0.

- The minimum supported version of `Pillow` is increased from 6.2.0 to 6.2.1.

- The minimum supported version of `jinja2` is increased from 2.9.2 to 2.11.0.

- The minimum supported version of redis-py is increased from 3.0.0 to 3.4.0.

- Manually instantiated `WSGIRequest` objects must be provided a file-like object for `wsgi.input`. Previously, Django was more lax than the expected behavior as specified by the WSGI specification.

- Support for `PROJ` < 5 is removed.

- `EmailBackend` now verifies a `hostname` and `certificates`. If you need the previous behavior that is less restrictive and not recommended, subclass `EmailBackend` and override the `ssl_context` property.

## Features deprecated in 4.2

### `index_together` option is deprecated in favor of `indexes`

The `Meta.index_together` option is deprecated in favor of the `indexes` option.

Migrating existing `index_together` should be handled as a migration. For example:

    class Author(models.Model):
        rank = models.IntegerField()
        name = models.CharField(max_length=30)

        class Meta:
            index_together = [["rank", "name"]]

Should become:

    class Author(models.Model):
        rank = models.IntegerField()
        name = models.CharField(max_length=30)

        class Meta:
            indexes = [models.Index(fields=["rank", "name"])]

Running the `makemigrations` command will generate a migration containing a `RenameIndex` operation which will rename the existing index. Next, consider squashing migrations to remove `index_together` from historical migrations.

The `AlterIndexTogether` migration operation is now officially supported only for pre-Django 4.2 migration files. For backward compatibility reasons, it’s still part of the public API, and there’s no plan to deprecate or remove it, but it should not be used for new migrations. Use `AddIndex` and `RemoveIndex` operations instead.

### Passing encoded JSON string literals to `JSONField` is deprecated

`JSONField` and its associated lookups and aggregates used to allow passing JSON encoded string literals which caused ambiguity on whether string literals were already encoded from database backend’s perspective.

During the deprecation period string literals will be attempted to be JSON decoded and a warning will be emitted on success that points at passing non-encoded forms instead.

Code that used to pass JSON encoded string literals:

    Document.objects.bulk_create(
        Document(data=Value("null")),
        Document(data=Value("[]")),
        Document(data=Value('"foo-bar"')),
    )
    Document.objects.annotate(
        JSONBAgg("field", default=Value("[]")),
    )

Should become:

    Document.objects.bulk_create(
        Document(data=Value(None, JSONField())),
        Document(data=[]),
        Document(data="foo-bar"),
    )
    Document.objects.annotate(
        JSONBAgg("field", default=[]),
    )

From Django 5.1+ string literals will be implicitly interpreted as JSON string literals.

### Miscellaneous

- The `BaseUserManager.make_random_password()` method is deprecated. See recipes and best practices for using Python’s `secrets` module to generate passwords.

- The `length_is` template filter is deprecated in favor of `length` and the `==` operator within an `{% if %}` tag. For example

      {% if value|length == 4 %}…{% endif %}
      {% if value|length == 4 %}True{% else %}False{% endif %}

  instead of:

      {% if value|length_is:4 %}…{% endif %}
      {{ value|length_is:4 }}

- `django.contrib.auth.hashers.SHA1PasswordHasher`, `django.contrib.auth.hashers.UnsaltedSHA1PasswordHasher`, and `django.contrib.auth.hashers.UnsaltedMD5PasswordHasher` are deprecated.

- `django.contrib.postgres.fields.CICharField` is deprecated in favor of `CharField(db_collation="…")` with a case-insensitive non-deterministic collation.

- `django.contrib.postgres.fields.CIEmailField` is deprecated in favor of `EmailField(db_collation="…")` with a case-insensitive non-deterministic collation.

- `django.contrib.postgres.fields.CITextField` is deprecated in favor of `TextField(db_collation="…")` with a case-insensitive non-deterministic collation.

- `django.contrib.postgres.fields.CIText` mixin is deprecated.

- The `map_height` and `map_width` attributes of `BaseGeometryWidget` are deprecated, use CSS to size map widgets instead.

- `SimpleTestCase.assertFormsetError()` is deprecated in favor of `assertFormSetError()`.

- `TransactionTestCase.assertQuerysetEqual()` is deprecated in favor of `assertQuerySetEqual()`.

- Passing positional arguments to `Signer` and `TimestampSigner` is deprecated in favor of keyword-only arguments.

- The `DEFAULT_FILE_STORAGE` setting is deprecated in favor of `STORAGES["default"]`.

- The `STATICFILES_STORAGE` setting is deprecated in favor of `STORAGES["staticfiles"]`.

- The `django.core.files.storage.get_storage_class()` function is deprecated.