[4.2.x] Fixed #34992 -- Fixed DatabaseFeatures.allows_group_by_selected_pks on MariaDB with ONLY_FULL_GROUP_BY sql mode.

Regression in 041551d716.

Backport of 0257426fe1 from main.

django/db/backends/mysql/features.py

@@ -6,7 +6,6 @@ from django.utils.functional import cached_property
 
 class DatabaseFeatures(BaseDatabaseFeatures):
     empty_fetchmany_value = ()
-    allows_group_by_selected_pks = True
     related_fields_match_type = True
     # MySQL doesn't support sliced subqueries with IN/ALL/ANY/SOME.
     allow_sliced_subqueries_with_in = False
@@ -348,3 +347,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         if self.connection.mysql_is_mariadb:
             return self.connection.mysql_version >= (10, 5, 2)
         return True
+
+    @cached_property
+    def allows_group_by_selected_pks(self):
+        if self.connection.mysql_is_mariadb:
+            return "ONLY_FULL_GROUP_BY" not in self.connection.sql_mode
+        return True

docs/releases/4.2.8.txt

@@ -27,3 +27,7 @@ Bugfixes
 
 * Fixed a regression in Django 4.2 where checkboxes in the admin would be
   centered on narrower screen widths (:ticket:`34994`).
+
+* Fixed a regression in Django 4.2 that caused a crash of querysets with
+  aggregations on MariaDB when the ``ONLY_FULL_GROUP_BY`` SQL mode was enabled
+  (:ticket:`34992`).

tests/backends/mysql/test_features.py

@@ -42,3 +42,21 @@ class TestFeatures(TestCase):
             _connection.sql_mode = {"NO_AUTO_VALUE_ON_ZERO"}
             database_features = DatabaseFeatures(_connection)
             self.assertIs(database_features.allows_auto_pk_0, True)
+
+    def test_allows_group_by_selected_pks(self):
+        with mock.MagicMock() as _connection:
+            _connection.mysql_is_mariadb = False
+            database_features = DatabaseFeatures(_connection)
+            self.assertIs(database_features.allows_group_by_selected_pks, True)
+
+        with mock.MagicMock() as _connection:
+            _connection.mysql_is_mariadb = False
+            _connection.sql_mode = {}
+            database_features = DatabaseFeatures(_connection)
+            self.assertIs(database_features.allows_group_by_selected_pks, True)
+
+        with mock.MagicMock() as _connection:
+            _connection.mysql_is_mariadb = True
+            _connection.sql_mode = {"ONLY_FULL_GROUP_BY"}
+            database_features = DatabaseFeatures(_connection)
+            self.assertIs(database_features.allows_group_by_selected_pks, False)