Codeigniter Update_batch不更新记录

Question

我想从表中更新model_quantity列值，而我的数组是::

  $data['update_models'][$i]=
     array(
        'model_quantity'=>'`model_quantity`-'.$_POST['quantity_row_'.$i],
        'model_name'=>addslashes($_POST['model_row_'.$i]),
      );
$this->db->update_batch('table_name',$data,'model_name');

Update_Batch无效我将最后执行的查询作为

UPDATE `model` SET `model_quantity` = CASE 
WHEN `model_name` = 'Road 100x250 5\\\"' THEN '`model_quantity`-2'
WHEN `model_name` = 'Road 100x250 5\\\"' THEN '`model_quantity`-1'
ELSE `model_quantity` END WHERE `model_name` IN ('Road 100x250 5\\\"','Road 100x250 5\\\"')

数组为

$data = Array
(
    [0] => Array
        (
            [model_quantity] => model_quantity-2
            [model_name] => Road 100x250 5\"
        )


[1] => Array
    (
        [model_quantity] => `model_quantity`-1
        [model_name] => Road 100x250 5\"
    )


)