Fix quotas migration failure

With sqlalchemy 0.7.2 and migrate 0.7.1, I was seeing:

   Traceback (most recent call last):
     File "/usr/lib/python2.7/site-packages/nova/db/migration.py", line 37, in db_sync
       ret = IMPL.db_sync(version=version)
     [..]
     File "/usr/lib/python2.7/site-packages/nova/db/sqlalchemy/migrate_repo/versions/016_make_quotas_key_and_value.py", line 189, in upgrade
       new_quotas.rename('quotas')
     [..]
     File "/usr/lib/python2.7/site-packages/migrate/changeset/schema.py", line 479, in deregister
       del meta.tables[key]
     File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/_collections.py", line 38, in _immutable
       raise TypeError("%s object is immutable" % self.__class__.__name__)
   TypeError: immutabledict object is immutable

This is actually a bug in sqlalchemy-migrate:

  http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=128

But it can be worked around by ensuring there isn't a 'quotas' table in
the metadata's table hash before renaming.

1 files changed, 14 insertions, 4 deletions

diff --git a/nova/db/sqlalchemy/migrate_repo/versions/016_make_quotas_key_and_value.py b/nova/db/sqlalchemy/migrate_repo/versions/016_make_quotas_key_and_value.py
index a4fe3e482..56b287171 100644
--- a/nova/db/sqlalchemy/migrate_repo/versions/016_make_quotas_key_and_value.py
+++ b/nova/db/sqlalchemy/migrate_repo/versions/016_make_quotas_key_and_value.py
@@ -75,8 +75,8 @@ def new_style_quotas_table(name):
                 )
 
 
-def existing_quotas_table(migrate_engine):
-    return Table('quotas', meta, autoload=True, autoload_with=migrate_engine)
+def quotas_table(migrate_engine, name='quotas'):
+    return Table(name, meta, autoload=True, autoload_with=migrate_engine)
 
 
 def _assert_no_duplicate_project_ids(quotas):
@@ -179,13 +179,18 @@ def upgrade(migrate_engine):
     # bind migrate_engine to your metadata
     meta.bind = migrate_engine
 
-    old_quotas = existing_quotas_table(migrate_engine)
+    old_quotas = quotas_table(migrate_engine)
     assert_old_quotas_have_no_active_duplicates(migrate_engine, old_quotas)
 
     new_quotas = new_style_quotas_table('quotas_new')
     new_quotas.create()
     convert_forward(migrate_engine, old_quotas, new_quotas)
     old_quotas.drop()
+
+    # clear metadata to work around this:
+    # http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=128
+    meta.clear()
+    new_quotas = quotas_table(migrate_engine, 'quotas_new')
     new_quotas.rename('quotas')
 
 
@@ -193,11 +198,16 @@ def downgrade(migrate_engine):
     # Operations to reverse the above upgrade go here.
     meta.bind = migrate_engine
 
-    new_quotas = existing_quotas_table(migrate_engine)
+    new_quotas = quotas_table(migrate_engine)
     assert_new_quotas_have_no_active_duplicates(migrate_engine, new_quotas)
 
     old_quotas = old_style_quotas_table('quotas_old')
     old_quotas.create()
     convert_backward(migrate_engine, old_quotas, new_quotas)
     new_quotas.drop()
+
+    # clear metadata to work around this:
+    # http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=128
+    meta.clear()
+    old_quotas = quotas_table(migrate_engine, 'quotas_old')
     old_quotas.rename('quotas')