API Performance

[gtanzillo]

Issues related to improving the performance of the ManageIQ Rest API

• Slow but small response for virtual columns seemingly due to N+1 queries
  • [renderer.rb] Don't re-Rbac: part deux: [renderer.rb] Don't re-Rbac: part deux #874
  • AR VirtualAttribute queries + introspection: [WIP] Add include_for_find support via 'expand' #877 AR VirtualAttribute queries + introspection #887 [Renderer] Handle :uses for :include_for_find #890
• Improve user login timings
  • _Use .update_attribute over .save! for User login:_ [WIP] Use .update_attribute over .save! for User login manageiq#20471
  • Reduce queries for User#save validations: For User, don't query groups if the groups did not change manageiq#20590
• Add support for returning nil/null in associations
• Querying for &attributes=hardware.cpu_sockets is 0.5 seconds faster than num_cpu, WAT