Flavor extra_specs extension mixed the flavor_id and instance_type_id

The nova database API use instance_type id as parameter to access flavor extra spec ( like instance_type_extra_specs_update_or_create in nova/db/api.py).

However, the nova API extension for flavor extra specs (nova/api/openstack/compute/contrib/flavorextraspecs.py) call the DB API using the flavor_id as instance type id, for example, creaet() call instance_type_extra_specs_update_or_create() with flavor_id.

Because the flavor_id and instance_type is different in most time, this is sure to cause trouble. I meet this when I try to add the flavor extra spec support to the python-novaclient.

We think there are three methods to handle it:
1) Translation from flavor_id to instance_type id in the Nova API extension. Thus keep no changes for DB API.
2) Add new APIs to nova DB (i.e. nova/db/api.py), to get/delete/update the extra spec through flavor_id, i.e. two set of APIs to operate the flavor extra specs.
3) Change current DB APIs to use flavor_id, instead of instance_type id. After all, instance_type id is mostly a DB internal id, but I'm not sure because nova/db/api.py, does expose the instance_type id through instance_type_get().

I created a patch with method 1, but not sure if that's the right solution, hope more input from community.

Thanks
--jyh