$this->db->affected_rows() returns -1 after query

[eluser]bleu[/eluser]
[quote author="Aken" date="1336375382"]Is the query you're generating correct? You can check using $this->db->last_query(). Are you running the affected_rows() method IMMEDIATELY after performing the query? If not, other DB manipulations may be altering the expected results.[/quote]

Yes the query I am generating correct($this->db->last_query() returns the same query I run manually in phpmyadmin) I have tried running it in phpmyadmin and it gives me the proper 0 or 1 rows affected as per the data.But when i run it through codeigniter I get -1

Is it because I have turned on codeigniter mysqli drivers