activerecord - .endmost scope - optimized .last

gistfile1.txt

.endmost is what you want when you call .last: the last N records in the result set without having to retrieve all records from the database, and it works with any ordering. You can impose filtering before, Message.where(…).in_order.endmost(10), and afterwards to filter your final results as well Message.in_order.endmost(10).where(…).

class Message
  class << self
    def in_order
      order(created_at: :asc)
    end

    def recent(n)
      in_order.endmost(n)
    end

    def endmost(n)
      all.only(:order).from(all.reverse_order.limit(n), table_name)
    end
  end
end


http://www.elabs.se/blog/72-retrieving-the-last-n-ordered-records-with-activerecord