Manager/GenericDocumentManager.php
public function countByGroup($fieldGroup, $match = [], $query = null, $sort = null, $limit = null)
    {
        $group = [
            '_id' => '$'.$fieldGroup,
            'count' => [ '$sum' => 1]
        ];

        return $this->aggregateGroup($group, $match, $query, $sort, $limit);
    }
public function countByGroup($fieldGroup, $match = [], $query = null, $sort = null, $limit = null)
    {
        $group = [
            '_id' => '$'.$fieldGroup,
            'count' => [ '$sum' => 1]
        ];

        return $this->aggregateGroup($group, $match, $query, $sort, $limit);
    }
Count items by group

@param mixed $collection
@param mixed $fieldGroup
@param mixed $match

@return array Multidimensional array with key => count per group