MySQL选择blob增加性能

Question

这个sql select对于大量数据来说太慢了，如何在mysql中提高它的运行速度？

SELECT c.car_id, o.start_date, own.name 
FROM Cars c
JOIN Orders o ON c.car_id = o.car_id 
JOIN Owner own ON o.order_id = own.owner_id 
WHERE c.wheel IS NOT NULL AND c.document IS NULL ORDER BY c.car_id DESC;

文档字段是blob。