Active record update with on_after_post() hook

Gumster · May 2012

I've got a photos / gallery model that uses on_after_post() to create thumbnails, and that aspect works fine. I thought I'd add to the functionality by saving the thumb filename to the table from on_after_post().

So I have this:

    function on_after_post($values)
    {

	$CI =& get_instance();
	$CI->load->library('image_lib');
	$pk = $values['id'];
		
	// create the thumbnail if an image is uploaded
	if (!empty($CI->upload))
	{
		$data = $CI->upload->data();
		if (!empty($data['full_path']))
		{		
			// create thumb
			$config = array();
			$config['create_thumb'] = TRUE;				
			$config['source_image'] = $data['full_path'];
			$config['width'] = 100;
			$config['height'] = 80;
			$config['master_dim'] = 'auto';
			$config['maintain_ratio'] = TRUE;
			$config['thumb_marker'] = '_thumb';
			$CI->image_lib->clear();
			$CI->image_lib->initialize($config);
			if (!$CI->image_lib->resize())
			{
				$this->add_error($CI->image_lib->display_errors());
			}
			else // store thumb filename for convenience
			{
				$thm = $data['raw_name'] . $config['thumb_marker'] . $data['file_ext'];
				$this->_update_thumb_field($pk, $thm);
				}
			}
		}
		return $values;
	}
	
	function _update_thumb_field($pk, $thm)
	{
		if(is_numeric($pk))
		{	
			$this->db->set('thumbnail_file', $thm);
			$this->db->set('id', $pk); /* without this, id gets set to 0 */
			$this->db->where('id', $pk);
			$this->db->update('photos');			
		}
	}

Now here's what I find odd - without the id being explicitly set(), the update leaves id as 0, and yet $pk is always the right index value for the table. In SQL terms that just seems unnecessary (eg UPDATE photos SET id = x, thumbnail_file = 'xyz_thumb.gif' WHERE id = x). Is doing an update from this hook likely to lead to any race conditions? This is more likely a MySQL issue or a Codeigniter one, but maybe I'm misunderstanding what can be done with on_after_post(). Incidentally, if this is the last hook to trigger (is it?) does there need to be a return for $values?

Gumster · May 2012

I worked out a more satisfactory way of getting Active Record to do what I wanted:


	function _update_thumb_field($pk, $thm)
	{
		if(is_numeric($pk))
		{	
			$where = 'id = '. $pk;
			$data = array('thumbnail_file' => $thm);
			$str = $this->db->update_string('photos', $data, $where);
			$this->db->query($str);
			$this->db->get('photos');
		}
	}

So that avoided having to over-write the id using set(), which offended me beyond reasonable measure.

I'd like to know why the update method seems to railroad me into that situation though.

admin · May 2012

There doesn't need to be a return of values. Could you do a $this->db->debug_query() right after $this->db->update('photos') to see what it outputs for the query?

Gumster · May 2012

Yup I did some debugging and the update() method was insisting on using SET `id` = '', and since there was no id being explicitly set, it found the right record, and overwrote the id with 0. Why it persisted in this I don't understand. I wonder if - ironically - it is because of some safety setting somewhere? Whether from CI or MySQL I'm not sure.

Still, the alternative is satisfactory.

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Active record update with on_after_post() hook

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