Codeigniter只执行一次模型

Question

我有一个控制器调用模型方法减去2个表。但是每次控制器在浏览器中访问时，模型func总是减去2表。如果其他表有变化，我想只是减去。我怎么能这样做？

控制器

function slots(){

        $totalpaid911 = $this->data->participantpaid911();
        $totalpaid1214 = $this->data->participantpaid1214();
        $totalpaidkapihan = $this->data->participantpaidkapihan();

        $paid = array('totalpaid911' => $totalpaid911,
                      'totalpaid1214' => $totalpaid1214,
                      'totalpaidkapihan' => $totalpaidkapihan);

        $test = $this->data->updateslottotal911($paid);

        $data['data'] = $this->data->slotstatus();

        $this->load->view('site/header',$data);
        $this->load->view('site/minicamp-slots',$data);
        $this->load->view('site/login-modal');
        $this->load->view('site/signup-modal');
        $this->load->view('site/footer');
}

模型

function updateslottotal911($paid){
    $this->db->select('slotavailable');
    $this->db->where('program','9-11 Mini Camp');
    $query = $this->db->get('tbl_slot_status');

    $result = $query->result();

    $slotavailable = $result['0']->slotavailable - $paid['totalpaid911']; 

    $data = array('slotavailable' => $slotavailable);

    $this->db->where('program','9-11 Mini Camp');
    $this->db->update('tbl_slot_status',$data); 


}

这里的codeigniter新手:(