# File ar-extensions/lib/ar-extensions/union.rb, line 170
    def construct_calculation_sql_with_extension(operation, column_name, options)
      construct_ar_extension_sql(options.merge(:command => '', :keywords => nil, :distinct => nil)) {|sql, o|
        calc_sql = construct_calculation_sql(operation, column_name, options)

        #this is really gross but prevents us from rewriting construct_calculation_sql
        calc_sql.gsub!(/^SELECT\s/, "SELECT #{options[:keywords]} ") if options[:keywords]

        sql << calc_sql
      }
    end