Mongo mapper use aggregation framework

[Muhammad Shahzad]

Hi,

Can someone please give me a example how I can sum a field using user id field?
https://fatfreeframework.com/3.6/mongo-mapper


Here is my code, this is returning me all documents matched with userId but not the sum.

 $f3 = \Base::instance();
$mapper = new \DB\Mongo\Mapper($f3->get('MongoDB'),'transactions');
        $filter = array('userId'=>$transArray['userId']);
        $options = array(
                  array(
                    'group' => array(
                        '_id' => array('userId' => $userId),
                        'systemGeneratedCashback' => array('$sum' => 'systemGeneratedCashback')
                    )
                  )
        );        
       $data =  $mapper->find($filter, $options);

       echo "<pre>";
       print_r($data);
       exit;

[ikkez]

maybe try it with map/reduce:

$options = array(
  'group => array(
      'keys' => array('userId' => 1),
      'reduce' => 'function (obj, prev) {cash_sum += obj.systemGeneratedCashback;}',
      'initial' => array('cash_sum' => 0),
      'finalize' => '',
  );
)