add_index_sql

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 787
      def add_index_sql(table_name, column_name, options = {})
        index_name, index_type, index_columns, _, index_algorithm, index_using = add_index_options(table_name, column_name, options)
        index_algorithm[0, 0] = ", " if index_algorithm.present?
        "ADD #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} (#{index_columns})#{index_algorithm}"
      end