msProducts и RAND, как оптимизировать?

{'!msProducts' | snippet: [
            'parents' => '528', 
            'tpl' => 'product-main',
            'includeTVs' => 'price_old,image,categ',
            'tvPrefix' => 'tv',
            'sortby' => 'RAND()',

SELECT f.id FROM files f
	    JOIN ( SELECT RAND() * (SELECT MAX(id) FROM files) AS max_id ) AS m
	    WHERE f.id >= m.max_id
	    ORDER BY f.id ASC
	    LIMIT 1;