private function FetchFields($res)
    {
        if (!$this->debug_on) {
            return ;
        }
        $i=0;
        $this->col_info = array();
        while ($i < @pg_num_fields($res)) {
            $this->col_info[$i]->name = @pg_field_name($res, $i);
            $this->col_info[$i]->size = @pg_field_size($res, $i);
            $this->col_info[$i]->type = @pg_field_type($res, $i);
            $i++;
        }
    }