SarasovMatvey

These error cause when i try to run following code: ``` php $collection = $this->getClient()->getDatabase($this->db)->getCollection('messages'); $pipeline = $collection->createAggregator()->setBatchSize(100)->group(array('_id' => '$channelId', 'sum' => array('$sum' => 1))); $result = $collection->aggregate($pipeline, array(), false);...