Getting the current state requires reading the whole DB

[Alberto Mardegan]

If a client wants to read the current state of all the applications registered in the store (like the Ubuntu System Settings security panel does) then it currently needs to read the whole DB, which also includes historical data.
The same applies to a client which want to get the state of a single application, if it doesn't know in advance which features are used by this store.

Possible solutions:
1) Discard the historical data: create a constraint on the uniqueness of the request's from+feature field combination, so that every record retrieved from the DB contains actual information.
2) Create a new API which only retrieves the latest records (= whose information is not obsoleted) and keep the existing API available for retrieving the historical data.

Personally, I think that having a timestamp on the request is enough information and the full history of the decisions is not required.