codeigniter how to check if database update su code example

Example: codeigniter how to know update failed

$this->db->trans_start();
$this->db->query('AN SQL QUERY...');
$this->db->update('table',$array);
$this->db->trans_complete();

if ($this->db->trans_status() === FALSE)
{
    // generate an error... or use the log_message() function to log your error
}