pg_search: ordering of "multisearchable" results

There is a simple answer but it does not work with "multisearchable".

First, I needed to change from "multisearchable" (which works with multiple models) to "pg_search_scope" (searches in a single model only).

Second, I needed to use :order_within_rank. Since the results are all 100% matches of the search term, they have the same ranking according to pg_search. :order_within_rank gives a secondary rank as a tiebreaker.

class Advert < ActiveRecord::Base

  include PgSearch
  pg_search_scope :search_by_full_advert, 
                  :against => [:title, :body],
                  :order_within_rank => "adverts.created_at DESC"

end