application_controller_mysql.rb

class ApplicationController < ActionController::Base
  before_filter :set_rand_cookie

  private
  
  def set_rand_cookie
    return if cookies[:rand_seed].present?
    cookies[:rand_seed] = {value: rand(100), expires: Time.now + 900}
  end
end

application_controller_postgres.rb

class ApplicationController < ActionController::Base
  before_filter :set_rand_cookie

  private
  
  def set_rand_cookie
    return if cookies[:rand_seed].present?
    cookies[:rand_seed] = {value: rand, expires: Time.now + 900}
  end
end

members_controller_mysql.rb

class MembersController < ApplicationController

  def index
    seed_val = Member.connection.quote(cookies[:rand_seed])
    @members = Member.order("RAND(#{seed_val})").page(params[:page]).per(15)
  end
  
end

members_controller_postgres.rb

class MembersController < ApplicationController

  def index
    seed_val = Member.connection.quote(cookies[:rand_seed])
    Member.connection.execute("select setseed(#{seed_val})")
    @members = Member.order('random()').page(params[:page]).per(15)
  end

end