Оптимизировать медленный запрос к БД Опенкарт

Категории открываются долго из-за этого запроса:
Info: SELECT p.product_id, (SELECT AVG(rating) AS total FROM oc_review r1 WHERE r1.product_id = p.product_id AND r1.status = '1' GROUP BY r1.product_id) AS rating, (SELECT price FROM oc_product_discount pd2 WHERE pd2.product_id = p.product_id AND pd2.customer_group_id = '1' AND pd2.quantity = '1' AND ((pd2.date_start = '0000-00-00' OR pd2.date_start  NOW())) ORDER BY pd2.priority ASC, pd2.price ASC LIMIT 1) AS discount, (SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '1' AND ((ps.date_start = '0000-00-00' OR ps.date_start  NOW())) ORDER BY ps.priority ASC, ps.price ASC LIMIT 1) AS special FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = '1' AND p.status = '1' AND p.date_available