Implement python version of migration 002.

This patch adds a python version of keystone migration 002 which
supports MySQL and PostgreSQL. SQLite still uses manual .sql files
for now...

Fixes LP Bug #1031164.

Change-Id: I2f4f7b0ea42040994bd8e1711ccbbb6d690c868f

keystone/common/sql/migrate_repo/versions/002_mysql_downgrade.sql

@@ -1,3 +0,0 @@
-alter table token drop id;
-alter table token change id_hash id varchar(64);
-

keystone/common/sql/migrate_repo/versions/002_mysql_upgrade.sql

@@ -1,2 +0,0 @@
-alter table token change id id_hash varchar(64);
-alter table token add id varchar(2048);

keystone/common/sql/migrate_repo/versions/002_token_id_hash.py

@@ -0,0 +1,43 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2012 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from sqlalchemy import Column, MetaData, String, Table
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+    token = Table('token', meta, autoload=True)
+    old_id_col = token.c.id
+    old_id_col.alter(name='id_hash')
+    # Note: We obtain a new metadata reference to avoid
+    # sqlalchemy.exc.ArgumentError:
+    # Trying to redefine primary-key column 'id' as a non-primary-key...
+    meta = MetaData()
+    meta.bind = migrate_engine
+    token = Table('token', meta, autoload=True)
+    new_id = Column("id", String(2048))
+    token.create_column(new_id)
+
+
+def downgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+    token = Table('token', meta, autoload=True)
+    token.drop_column('id')
+    token = Table('token', meta, autoload=True)
+    id_col = token.c.id_hash
+    id_col.alter(name='id')