Fixed #28794 -- Fixed tx_isolation deprecation warning on MySQL 5.7.20+.

django/db/backends/mysql/base.py

@@ -222,7 +222,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                         ', '.join("'%s'" % s for s in sorted(self.isolation_levels))
                     ))
             # The variable assignment form of setting transaction isolation
-            # levels will be used, e.g. "set tx_isolation='repeatable-read'".
+            # levels will be used, e.g. "set transaction_isolation='repeatable-read'".
             isolation_level = isolation_level.replace(' ', '-')
         self.isolation_level = isolation_level
         kwargs.update(options)
@@ -231,6 +231,10 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     def get_new_connection(self, conn_params):
         return Database.connect(**conn_params)
 
+    @cached_property
+    def transaction_isolation_variable(self):
+        return 'tx_isolation' if self.mysql_version < (5, 7, 20) else 'transaction_isolation'
+
     def init_connection_state(self):
         assignments = []
         if self.features.is_sql_auto_is_null_enabled:
@@ -241,7 +245,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             assignments.append('SQL_AUTO_IS_NULL = 0')
 
         if self.isolation_level:
-            assignments.append("TX_ISOLATION = '%s'" % self.isolation_level)
+            assignments.append("%s = '%s'" % (self.transaction_isolation_variable, self.isolation_level))
 
         if assignments:
             with self.cursor() as cursor:

tests/backends/mysql/tests.py

@@ -38,7 +38,7 @@ class IsolationLevelTests(TestCase):
     @staticmethod
     def get_isolation_level(connection):
         with connection.cursor() as cursor:
-            cursor.execute("SELECT @@session.tx_isolation")
+            cursor.execute("SELECT @@session.%s" % connection.transaction_isolation_variable)
             return cursor.fetchone()[0]
 
     def test_auto_is_null_auto_config(self):