l have a problem that l need to close be_debug at the only one of the request.
on this, l want to catch the db_error myself and then to do something.
for example:
// now 'db_debug' option is true in database.php
$this->db->trans_begin(true);
$this->db->query('select * from `not_exist_table`');
$st = $this->db->trans_status();
if($st === false){
// ...
}