static int

join_read_always_key(JOIN_TAB *tab)

{

  int error;

  TABLE *table= tab->table;

  /* Initialize the index first */

  if (!table->file->inited)

  {

    if (unlikely((error= table->file->ha_index_init(tab->ref.key,

                                                    tab->sorted))))

    {

      (void) report_error(table, error);

      return 1;

    }

  }

  if (unlikely(cp_buffer_from_ref(tab->join->thd, table, &tab->ref)))

    return -1;

  if (unlikely((error=

                table->file->prepare_index_key_scan_map(tab->ref.key_buff,

                                                        make_prev_keypart_map(tab->ref.key_parts)))))