Ticket #16961: ticket_16961.diff.3

diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index c1ef625..bacd998 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -261,15 +261,17 @@ class DatabaseOperations(BaseDatabaseOperations):
                 sql.append('%s %s;' % (style.SQL_KEYWORD('TRUNCATE'), style.SQL_FIELD(self.quote_name(table))))
             sql.append('SET FOREIGN_KEY_CHECKS = 1;')
 
-            # 'ALTER TABLE table AUTO_INCREMENT = 1;'... style SQL statements
-            # to reset sequence indices
-            sql.extend(["%s %s %s %s %s;" % \
-                (style.SQL_KEYWORD('ALTER'),
-                 style.SQL_KEYWORD('TABLE'),
-                 style.SQL_TABLE(self.quote_name(sequence['table'])),
-                 style.SQL_KEYWORD('AUTO_INCREMENT'),
-                 style.SQL_FIELD('= 1'),
-                ) for sequence in sequences])
+            # Truncate already resets the AUTO_INCREMENT field from
+            # MySQL version 5.0.13 onwards. Refs #16961.
+            if self.connection.mysql_version < (5,0,13):
+                sql.extend(
+                    ["%s %s %s %s %s;" % \
+                     (style.SQL_KEYWORD('ALTER'),
+                      style.SQL_KEYWORD('TABLE'),
+                      style.SQL_TABLE(self.quote_name(sequence['table'])),
+                      style.SQL_KEYWORD('AUTO_INCREMENT'),
+                      style.SQL_FIELD('= 1'),
+                     ) for sequence in sequences])
             return sql
         else:
             return []
diff --git a/tests/regressiontests/backends/tests.py b/tests/regressiontests/backends/tests.py
index d5b1ea8..f87b9c4 100644
--- a/tests/regressiontests/backends/tests.py
+++ b/tests/regressiontests/backends/tests.py
@@ -61,10 +61,34 @@ class OracleChecks(unittest.TestCase):
     def test_client_encoding(self):
         # If the backend is Oracle, test that the client encoding is set
         # correctly.  This was broken under Cygwin prior to r14781.
-        c = connection.cursor()  # Ensure the connection is initialized.
+        connection.cursor()  # Ensure the connection is initialized.
         self.assertEqual(connection.connection.encoding, "UTF-8")
         self.assertEqual(connection.connection.nencoding, "UTF-8")
 
+class MySQLTests(TestCase):
+    @unittest.skipUnless(connection.vendor == 'mysql',
+                        "Test valid only for MySQL")
+    def test_autoincrement(self):
+        """
+        Check that auto_increment fields are reset correctly by sql_flush().
+        Before MySQL version 5.0.13 TRUNCATE did not do auto_increment reset.
+        Refs #16961.
+        """
+        statements = connection.ops.sql_flush(no_style(),
+                                              tables=['test'],
+                                              sequences=[{
+                                                  'table': 'test',
+                                                  'col': 'somecol',
+                                              }])
+        found_reset = False
+        for sql in statements:
+            found_reset = found_reset or 'ALTER TABLE' in sql
+        if connection.mysql_version < (5,0,13):
+            self.assertTrue(found_reset)
+        else:
+            self.assertFalse(found_reset)
+
+ 
 class DateQuotingTest(TestCase):
 
     def test_django_date_trunc(self):
diff --git a/tests/regressiontests/test_runner/models.py b/tests/regressiontests/test_runner/models.py
index e69de29..9a072e6 100644
--- a/tests/regressiontests/test_runner/models.py
+++ b/tests/regressiontests/test_runner/models.py
@@ -0,0 +1,5 @@
+from django.db import models
+
+class Person(models.Model):
+    first_name = models.CharField(max_length=20)
+    last_name = models.CharField(max_length=20)
diff --git a/tests/regressiontests/test_runner/tests.py b/tests/regressiontests/test_runner/tests.py
index ccb65b4..3fc8d7f 100644
--- a/tests/regressiontests/test_runner/tests.py
+++ b/tests/regressiontests/test_runner/tests.py
@@ -8,13 +8,15 @@ from optparse import make_option
 from django.core.exceptions import ImproperlyConfigured
 from django.core.management import call_command
 from django import db
-from django.test import simple
+from django.db import connection
+from django.test import simple, TransactionTestCase
 from django.test.simple import DjangoTestSuiteRunner, get_tests
 from django.test.testcases import connections_support_transactions
 from django.utils import unittest
 from django.utils.importlib import import_module
 
 from ..admin_scripts.tests import AdminScriptTestCase
+from .models import Person
 
 
 TEST_APP_OK = 'regressiontests.test_runner.valid_app.models'
@@ -262,3 +264,24 @@ class Sqlite3InMemoryTestDbs(unittest.TestCase):
                 self.assertTrue(connections_support_transactions(), msg)
             finally:
                 db.connections = old_db_connections
+
+
+class AutoIncrementResetTest(TransactionTestCase):
+    """
+    Here we test creating the same model two times in different test methods,
+    and check that both times they get "1" as their PK value. That is, we test
+    that AutoField values start from 1 for each transactional test case.
+    """
+    @unittest.skipIf(connection.vendor == 'oracle',
+                     "Oracle's auto-increment fields are not reset between "
+                     "tests")
+    def test_autoincrement_reset1(self):
+        p = Person.objects.create(first_name='Jack', last_name='Smith')
+        self.assertEquals(p.pk, 1)
+    
+    @unittest.skipIf(connection.vendor == 'oracle',
+                     "Oracle's auto-increment fields are not reset between "
+                     "tests")
+    def test_autoincrement_reset2(self):
+        p = Person.objects.create(first_name='Jack', last_name='Smith')
+        self.assertEquals(p.pk, 1)