// Constructors with an externally provided item name

  Item_string(THD *thd, const char *name_par, const char *str, size_t length,

              CHARSET_INFO *cs, Derivation dv= DERIVATION_COERCIBLE)

   :Item_literal(thd)

  {

    str_value.set_or_copy_aligned(str, length, cs);

    fix_from_value(dv, Metadata(&str_value));

    set_name(thd, name_par,safe_strlen(name_par), system_charset_info);

  }

  Item_string(THD *thd, const char *name_par, const char *str, size_t length,

              CHARSET_INFO *cs, Derivation dv, uint repertoire)

   :Item_literal(thd)

  {

    str_value.set_or_copy_aligned(str, length, cs);

    fix_from_value(dv, Metadata(&str_value, repertoire));

    set_name(thd, name_par, safe_strlen(name_par), system_charset_info);

  }

  Item_blob(THD *thd, const char *name_arg, uint length):

    Item_partition_func_safe_string(thd, name_arg, (uint) safe_strlen(name_arg),

                                    &my_charset_bin)

  { max_length= length; }

  Item_empty_string(THD *thd, const char *header,uint length,

                    CHARSET_INFO *cs= NULL):

    Item_partition_func_safe_string(thd, "", 0,

                                    cs ? cs : &my_charset_utf8_general_ci)

    {

      name.str=    header;

      name.length= strlen(name.str);

      max_length= length * collation.collation->mbmaxlen;

    }

void set_name(THD *thd, const LEX_CSTRING &str, CHARSET_INFO *cs= system_charset_info)

{

   set_name(thd, str.str, str.length, cs);

}

     field->set_name(thd, field_info->old_name,

                     strlen(field_info->old_name),

                     system_charset_info);

  LEX_CSTRING get_name() const

  {

    return LEX_CSTRING({field_name, strlen(field_name)});

  }

  LEX_CSTRING get_old_name() const

  {

    return LEX_CSTRING({old_name, strlen(old_name)});

  }