Suggest solution to search an object's array in Riak, using ActiveDocument + js map function

gistfile1.aw

<?php

use \ext\activedocument\Criteria;

$criteria = new Criteria;
$criteria->addColumnCondition(array('slug'=>$slug));
$category = Category::model()->find($criteria);

$criteria = new Criteria;
$criteria->order='updated ASC';
$criteria->addMapPhase('
function(value, keyData, arg) {
  if(!value["not_found"]) {
    var object = Riak.mapValuesJson(value)[0];
    if(object.hasOwnProperty(arg.col) && object[arg.col] instanceof Array) {
      if(object[arg.col].indexOf(arg.val) != -1)
        return [[value.bucket,value.key]];
    }
  }
  return [];
}
', array('arg' => array('col'=>'categories','val'=>$category->primaryKey)));

$apps = App::model()->findAll($criteria);