Fixed #29209 -- Fixed Cast() with TextField on MySQL and Oracle.

django/db/backends/mysql/operations.py

@@ -18,6 +18,7 @@ class DatabaseOperations(BaseDatabaseOperations):
     }
     cast_data_types = {
         'CharField': 'char(%(max_length)s)',
+        'TextField': 'char',
         'IntegerField': 'signed integer',
         'BigIntegerField': 'signed integer',
         'SmallIntegerField': 'signed integer',

django/db/backends/oracle/operations.py

@@ -51,6 +51,9 @@ END;
 
     # Oracle doesn't support string without precision; use the max string size.
     cast_char_field_without_max_length = 'NVARCHAR2(2000)'
+    cast_data_types = {
+        'TextField': cast_char_field_without_max_length,
+    }
 
     def cache_key_culling_sql(self):
         return """

tests/db_functions/test_cast.py

@@ -74,3 +74,6 @@ class CastTests(TestCase):
         """
         list(Author.objects.annotate(cast_float=Cast(Avg('age'), models.FloatField())))
         self.assertIn('(AVG("db_functions_author"."age"))::double precision', connection.queries[-1]['sql'])
+
+    def test_cast_to_text_field(self):
+        self.assertEqual(Author.objects.values_list(Cast('age', models.TextField()), flat=True).get(), '1')