Active Admin: sorting on multiple columns

This is also a monkey patch:

Create a new file in config/initializers or in the lib folder: multiple_columns_sorting.rb

module ActiveAdmin
  class ResourceController < BaseController
    module DataAccess
      def apply_sorting(chain)
        params[:order] ||= active_admin_config.sort_order

        orders = []
        params[:order].split('_and_').each do |fragment|
          order_clause = OrderClause.new fragment
          if order_clause.valid?
            orders << order_clause.to_sql(active_admin_config)
          end
        end

        if orders.empty?
          chain
        else
          chain.reorder(orders.shift).order(orders)
        end
      end
    end
  end
end

Restart the server. Now you can use several columns name separeted by "_and_". For example:

config.sort_order = 'first_name_desc_and_last_name_asc'