Rails ActiveRecord - querying on last record of relationship

I have a model Book with a has_many relationship to State.

class Book < ActiveRecord::Base
   has_many :states
   ...
end

State sets the visibility of the book to "private", "restricted" or "public" through a name attribute. For auditing purposes, we keep a record of all state changes so to get the current state of a book I use

> book = Book.first
> book.states.last.name
> "public"

Now I need to query on all Book objects where the current state is public.

Something along the lines of:

Book.joins(:visibility_states).where(states: { state: "public"})

The problem is that the query above return all books that are currently pubic, or have been public in the past. I only want it to return books that are currently "public" (i.e. book.states.last.name == "public").

I know I can do it with select but that's generating one query for each record:

Book.all.select { |b| b.states.last.name == "public" }

Is there a way to do it using ActiveRecord only?

via Chebli Mohamed