instance method conditions_tables

# File activerecord/lib/active_record/associations.rb, line 1728
        def conditions_tables(options)
          # look in both sets of conditions
          conditions = [scope(:find, :conditions), options[:conditions]].inject([]) do |all, cond|
            case cond
              when nil   then all
              when Array then all << cond.first
              else            all << cond
            end
          end
          conditions.join(' ').scan(/([\.a-zA-Z_]+).?\./).flatten
        end