MySQL Bugs: #8548: Request for a means to get the length of a field in chars instead of bytes

Bug #8548	Request for a means to get the length of a field in chars instead of bytes
Submitted:	16 Feb 2005 15:39	Modified:	11 Apr 2018 10:53
Reporter:	Matthew Lord	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Charsets	Severity:	S4 (Feature request)
Version:	all	OS:	Any (all)
Assigned to:	Geir Høydalsvik	CPU Architecture:	Any

Description:
I understand that the length field in the MYSQL_FIELD structure will probably not be changed as it has been in bytes for so long but there should be some means to get the length in characters for 
multi-byte columns.

How to repeat:
Create a UTF8 table, populate it with a few rows and check the lengths.

I know this is a poor example of how to repeat the problem but this is a known
and documented problem.

Suggested fix:
It could be another variable in the MYSQL_FIELD struct or another set of functions altogether so long as this functionality is available.

I don't think we really need a separate new field in the MYSQL_FIELD structure.
This simple function returns length of MYSQL_FIELD in characters:

/*
  Convert byte length to character length
*/
unsigned long
mysql_field_character_length(MYSQL_FIELD *field)
{
  CHARSET_INFO *cs;
  return  (cs= get_charset(fied->charsetnr)) ? field->length / cs->mbmaxlen : field->length;
}

Perhaps, instead of a new field in MYSQL_FIELD,
we should add this function into MySQL client library.

Fixed in 5.5+