code: func validateCommentLength(vars *variable.SessionVars, comment string, maxLen int, err error) (string, error) {
  	if len(comment) > maxLen {
  		if vars.StrictSQLMode {
  			return "", err
  		}
  		vars.StmtCtx.AppendWarning(err)
  		return comment[:maxLen], nil
  	}
  	return comment, nil
  }
docs: // validateCommentLength checks comment length of table, column, index and partition.
  // If comment length is more than the standard length truncate it
  // and store the comment length upto the standard comment length size.