From a88b8d8dcbbdfc1ddcda29bbffbaa44fd149b93a Mon Sep 17 00:00:00 2001
From: Sathish Nagappan <sathish.nagappan@nebula.com>
Date: Thu, 4 Oct 2012 02:27:20 -0700
Subject: [PATCH] implements selecting version in db sync

Fixes Bug #993284

db_sync compares the current version with the specified version
and upgrades or downgrades accordingly.

Change-Id: If0e0608ac04c264df7964f8cf6a46e9b156eee49
---
 glance/db/sqlalchemy/migration.py    | 12 +++++++-----
 glance/tests/unit/test_migrations.py | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/glance/db/sqlalchemy/migration.py b/glance/db/sqlalchemy/migration.py
index 7264e098..2c7cd8c3 100644
--- a/glance/db/sqlalchemy/migration.py
+++ b/glance/db/sqlalchemy/migration.py
@@ -119,12 +119,14 @@ def db_sync(version=None, current_version=None):
     try:
         _version_control(current_version or 0)
     except versioning_exceptions.DatabaseAlreadyControlledError, e:
-        if current_version is not None:
-            msg = (_("database '%(sql_connection)s' is already under "
-                     "migration control") % locals())
-            raise exception.DatabaseMigrationError(msg)
+        pass
 
-    upgrade(version=version)
+    if current_version is None:
+        current_version = int(db_version())
+    if version is not None and int(version) < current_version:
+        downgrade(version=version)
+    elif version is None or int(version) > current_version:
+        upgrade(version=version)
 
 
 def get_migrate_repo_path():
diff --git a/glance/tests/unit/test_migrations.py b/glance/tests/unit/test_migrations.py
index e833e9e7..f03fbc18 100644
--- a/glance/tests/unit/test_migrations.py
+++ b/glance/tests/unit/test_migrations.py
@@ -211,6 +211,20 @@ class TestMigrations(utils.BaseTestCase):
             cur_version = migration_api.db_version()
             self.assertEqual(cur_version, version)
 
+    def test_db_sync(self):
+        initial_version = 0
+        migration_api.db_sync(initial_version)
+        cur_version = migration_api.db_version()
+        self.assertEqual(cur_version, initial_version)
+
+        migration_api.db_sync(TestMigrations.REPOSITORY.latest)
+        cur_version = migration_api.db_version()
+        self.assertEqual(cur_version, TestMigrations.REPOSITORY.latest)
+
+        migration_api.db_sync(initial_version)
+        cur_version = migration_api.db_version()
+        self.assertEqual(cur_version, initial_version)
+
     def test_no_data_loss_2_to_3_to_2(self):
         """
         Here, we test that in the case when we moved a column "type" from the