I am using Ruby on Rails 3.2.2 and MySQL. After my previous question on "how to handle massive storage of records in database for user authorization purposes", since related answers (on how to solve the issue or how to accomplish to that I am looking for) aren't sufficiently detailed or require to much resources (at least for me), I would like to know what are valid and reasonable alternatives to that approach.

In few words, this question could be phrase as: how to handle "complex" (at level of SQL querying) user authorizations when you have to fetch "authorized" records? That is, for example, how to retrieve records when you would use code like the following (the following code would be used mostly in index controller actions):

Article.readable_by_user(@current_user)
# => Returns all articles readable by the current user.