# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 621
      def add_index_sql(table_name, column_name, options = {})
        index_name, index_type, index_columns = add_index_options(table_name, column_name, options)
        "ADD #{index_type} INDEX #{index_name} (#{index_columns})"
      end