Unified limits consists of registered limits and limits, which are project-specific. Both types are isolated into separate database tables (keystone.registered_limit and keystone.limit). The following is the existing schema for both tables:
http://paste.openstack.org/raw/723936/
There are some duplicated attributes between these two tables that are requirements for the API (e.g. a limit cannot be created without a corresponding limit being registered first). We have the opportunity to simplify the schema of the keystone.limit table by removing limit.service_id, limit.region_id, and limit.resource_name in favor of a single column called limit.registered_limit_id that maintains a FK relationship to a record in keystone.registered_limit.
The unified limit API will use the FK relationship to populate service_id, region_id, and resource_name attributes of a limit from the corresponding registered_limit.
Possibly solutions for the migration were whiteboarded using the following etherpad:
https://etherpad.openstack.org/p/keystone-unified-limit-migration-notepad
Fix proposed to branch: master
Review: https:/