Remove race condition (in Networks)

Soft delete all duplicate rows with the same vlan except one with
the biggest value in `id` column.

Create UC on fields (vlan, deleted)

Replace Select then Insert -> Try to Insert.

Fix error in network_update method. We were able to update
vlan to duplicate.

Fix typo in description of method drop_old_duplicate_entries_from_table()

blueprint db-enforce-unique-keys

Change-Id: Ia1b58ab5a5e369a1939de0b5c2f89aee6fc2c40b

nova/tests/test_db_api.py

@@ -334,6 +334,16 @@ class DbApiTestCase(test.TestCase):
         self.assertRaises(exception.DuplicateVlan,
                           db.network_create_safe, ctxt, values2)
 
+    def test_network_update_with_duplicate_vlan(self):
+        ctxt = context.get_admin_context()
+        values1 = {'host': 'localhost', 'project_id': 'project1', 'vlan': 1}
+        values2 = {'host': 'something', 'project_id': 'project1', 'vlan': 2}
+        network_ref = db.network_create_safe(ctxt, values1)
+        db.network_create_safe(ctxt, values2)
+        self.assertRaises(exception.DuplicateVlan,
+                          db.network_update,
+                          ctxt, network_ref["id"], values2)
+
     def test_instance_update_with_instance_uuid(self):
         # test instance_update() works when an instance UUID is passed.
         ctxt = context.get_admin_context()

nova/tests/test_migrations.py

@@ -860,6 +860,26 @@ class TestNovaMigrations(BaseMigrationTestCase):
         # recheck the 149 data
         self._check_149(engine, data)
 
+    def _prerun_158(self, engine):
+        networks = get_table(engine, 'networks')
+        data = [
+            {'vlan': 1, 'deleted': 0},
+            {'vlan': 1, 'deleted': 0},
+            {'vlan': 1, 'deleted': 0},
+        ]
+
+        for item in data:
+            networks.insert().values(item).execute()
+        return data
+
+    def _check_158(self, engine, data):
+        networks = get_table(engine, 'networks')
+        rows = networks.select().\
+                    where(networks.c.deleted != networks.c.id).\
+                    execute().\
+                    fetchall()
+        self.assertEqual(len(rows), 1)
+
 
 class TestBaremetalMigrations(BaseMigrationTestCase):
     """Test sqlalchemy-migrate migrations."""