Fixed #18392 -- Changed default mysql encoding to "utf8mb4".

django/db/backends/mysql/base.py

@@ -215,7 +215,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     def get_connection_params(self):
         kwargs = {
             "conv": django_conversions,
-            "charset": "utf8",
+            "charset": "utf8mb4",
         }
         settings_dict = self.settings_dict
         if settings_dict["USER"]:

django/db/backends/mysql/features.py

@@ -71,21 +71,11 @@ class DatabaseFeatures(BaseDatabaseFeatures):
 
     @cached_property
     def test_collations(self):
-        charset = "utf8"
-        if (
-            self.connection.mysql_is_mariadb
-            and self.connection.mysql_version >= (10, 6)
-        ) or (
-            not self.connection.mysql_is_mariadb
-            and self.connection.mysql_version >= (8, 0, 30)
-        ):
-            # utf8 is an alias for utf8mb3 in MariaDB 10.6+ and MySQL 8.0.30+.
-            charset = "utf8mb3"
         return {
-            "ci": f"{charset}_general_ci",
+            "ci": "utf8mb4_general_ci",
-            "non_default": f"{charset}_esperanto_ci",
+            "non_default": "utf8mb4_esperanto_ci",
-            "swedish_ci": f"{charset}_swedish_ci",
+            "swedish_ci": "utf8mb4_swedish_ci",
-            "virtual": f"{charset}_esperanto_ci",
+            "virtual": "utf8mb4_esperanto_ci",
         }
 
     test_now_utc_template = "UTC_TIMESTAMP(6)"
@@ -99,10 +89,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
                 "db_functions.comparison.test_least.LeastTests."
                 "test_coalesce_workaround",
             },
-            "Running on MySQL requires utf8mb4 encoding (#18392).": {
-                "model_fields.test_textfield.TextFieldTests.test_emoji",
-                "model_fields.test_charfield.TestCharField.test_emoji",
-            },
             "MySQL doesn't support functional indexes on a function that "
             "returns JSON": {
                 "schema.tests.SchemaTests.test_func_index_json_key_transform",

docs/ref/contrib/auth.txt

@@ -30,10 +30,7 @@ Fields
 
         The ``max_length`` should be sufficient for many use cases. If you need
         a longer length, please use a :ref:`custom user model
-        <specifying-custom-user-model>`. If you use MySQL with the ``utf8mb4``
+        <specifying-custom-user-model>`.
-        encoding (recommended for proper Unicode support), specify at most
-        ``max_length=191`` because MySQL can only create unique indexes with
-        191 characters in that case by default.
 
     .. attribute:: first_name
 

docs/ref/databases.txt

@@ -517,7 +517,7 @@ You can `create your database`_ using the command-line tools and this SQL:
 
 .. code-block:: sql
 
-  CREATE DATABASE <dbname> CHARACTER SET utf8;
+  CREATE DATABASE <dbname> CHARACTER SET utf8mb4;
 
 This ensures all tables and columns will use UTF-8 by default.
 
@@ -542,21 +542,21 @@ Django doesn't provide an API to change them.
 .. _documented thoroughly: https://dev.mysql.com/doc/refman/en/charset.html
 
 By default, with a UTF-8 database, MySQL will use the
-``utf8_general_ci`` collation. This results in all string equality
+``utf8mb4_0900_ai_ci`` collation. This results in all string equality
 comparisons being done in a *case-insensitive* manner. That is, ``"Fred"`` and
 ``"freD"`` are considered equal at the database level. If you have a unique
 constraint on a field, it would be illegal to try to insert both ``"aa"`` and
 ``"AA"`` into the same column, since they compare as equal (and, hence,
 non-unique) with the default collation. If you want case-sensitive comparisons
 on a particular column or table, change the column or table to use the
-``utf8_bin`` collation.
+``utf8mb4_0900_as_cs`` collation.
 
 Please note that according to `MySQL Unicode Character Sets`_, comparisons for
-the ``utf8_general_ci`` collation are faster, but slightly less correct, than
+the ``utf8mb4_general_ci`` collation are faster, but slightly less correct,
-comparisons for ``utf8_unicode_ci``. If this is acceptable for your application,
+than comparisons for ``utf8mb4_unicode_ci``. If this is acceptable for your
-you should use ``utf8_general_ci`` because it is faster. If this is not acceptable
+application, you should use ``utf8mb4_general_ci`` because it is faster. If
-(for example, if you require German dictionary order), use ``utf8_unicode_ci``
+this is not acceptable (for example, if you require German dictionary order),
-because it is more accurate.
+use ``utf8mb4_unicode_ci`` because it is more accurate.
 
 .. _MySQL Unicode Character Sets: https://dev.mysql.com/doc/refman/en/charset-unicode-sets.html
 
@@ -602,7 +602,7 @@ Here's a sample configuration which uses a MySQL option file::
     database = NAME
     user = USER
     password = PASSWORD
-    default-character-set = utf8
+    default-character-set = utf8mb4
 
 Several other `MySQLdb connection options`_ may be useful, such as ``ssl``,
 ``init_command``, and ``sql_mode``.

docs/releases/5.2.txt

@@ -174,7 +174,9 @@ CSRF
 Database backends
 ~~~~~~~~~~~~~~~~~
 
-* ...
+* MySQL connections now default to using the ``utf8mb4`` character set,
+  instead of ``utf8``, which is an alias for the deprecated character set
+  ``utf8mb3``.
 
 Decorators
 ~~~~~~~~~~
@@ -385,6 +387,14 @@ Dropped support for PostgreSQL 13
 Upstream support for PostgreSQL 13 ends in November 2025. Django 5.2 supports
 PostgreSQL 14 and higher.
 
+Changed MySQL connection character set default
+----------------------------------------------
+
+MySQL connections now default to using the ``utf8mb4`` character set, instead
+of ``utf8``, which is an alias for the deprecated character set ``utf8mb3``.
+``utf8mb3`` can be specified in the ``OPTIONS`` part of the ``DATABASES``
+setting, if needed for legacy databases.
+
 Miscellaneous
 -------------
 

tests/dbshell/test_mysql.py

@@ -112,7 +112,7 @@ class MySqlDbshellCommandTestCase(SimpleTestCase):
             "--user=someuser",
             "--host=somehost",
             "--port=444",
-            "--default-character-set=utf8",
+            "--default-character-set=utf8mb4",
             "somedbname",
         ]
         expected_env = {"MYSQL_PWD": "somepassword"}
@@ -124,7 +124,7 @@ class MySqlDbshellCommandTestCase(SimpleTestCase):
                     "PASSWORD": "somepassword",
                     "HOST": "somehost",
                     "PORT": 444,
-                    "OPTIONS": {"charset": "utf8"},
+                    "OPTIONS": {"charset": "utf8mb4"},
                 }
             ),
             (expected_args, expected_env),