SS4 How to sort a DataObject by COUNT of many_many relation (Updated version of http://www.silverstrip.es/blog/sort-tags-by-popularity-or-how-to-sort-a-dataobject-by-count-of-many-many-relation/)

SomePageController.php

 /**
     * Return a DataList of Example DataObjects sorted by the number
     * of Other records they are related to
     *
     * Note: This method will also filter out any Example DataObjects that aren't
     * related to any Other records
     *
     * @param integer $limit The maximum records to return
     * @return DataList Filtered DataList of Example DataObjects
     */
    public function getCategoryList($limit = 20)
    {
       $dataList = Example::get()
        ->setQueriedColumns(['ID', 'Title', 'Count(Example_Other_Many_Many_Table.Example_TableID)'])
        ->leftJoin('Example_Other_Many_Many_Table','Example_Other_Many_Many_Table.Example_TableID = Example_Table.ID')
        ->sort('Count(Example_Other_Many_Many_Table.Example_TableID) DESC')
        ->alterDataQuery(function($query){
            $query->groupBy('Example_Table.ID')
                  ->having('Count(Example_Other_Many_Many_Table.Example_TableID) > 0');
        })
        ->limit($limit);

        return $dataList;
    }