However there are many other nova migrations which don't even attempt. Have a look at 030 (multi nic) which just throws an a data loss exception. I'm not sure there is always a good solution when performing the downgrades however I do agree that we should always attempt to do them.
Fixing migration 031 is easy enough:
+ # grab tables virtual_ interfaces' , meta, autoload=True)
+ fixed_ips = Table('fixed_ips', meta, autoload=True)
+ virtual_interfaces = Table('
See the attached patch too....
However there are many other nova migrations which don't even attempt. Have a look at 030 (multi nic) which just throws an a data loss exception. I'm not sure there is always a good solution when performing the downgrades however I do agree that we should always attempt to do them.