Get Habari posts ordered by how many comments they have

gistfile1.php

		$presets['most_comments'] = array(
			'on_query_built' => function(Query $query) {
				$query->join('LEFT JOIN {comments} c ON c.post_id = {posts}.id');
				$query->groupby('{posts}.id');
				$query->orderby('count(c.id) DESC');
			}
		);