redis与mysql的数据一致性问题（并发更新）

# Python代码示例 - 使用Redis的WATCH和MULTI命令实现乐观锁
import redis
def purchase_item(user_id, product_id):
    redis_client = redis.StrictRedis(host='localhost', port=6379, db=0)
    with redis_client.pipeline() as pipe:
        while True:
            try:
                # 监视商品库存
                pipe.watch(f'product:{product_id}:stock')
                # 获取当前库存
                current_stock = int(pipe.get(f'product:{product_id}:stock') or 0)
                if current_stock > 0:
                    # 开始Redis事务
                    pipe.multi()
                    # 扣减库存
                    pipe.decr(f'product:{product_id}:stock')
                    # 执行Redis事务
                    pipe.execute()
                    # 购买成功
                    print(f"User {user_id} purchased product {product_id}. Remaining stock: {current_stock - 1}")
                    break
                else:
                    # 库存不足，取消监视，退出循环
                    pipe.unwatch()
                    print(f"User {user_id} attempted to purchase product {product_id}, but it's out of stock.")
                    break
            except redis.WatchError:
                # 被监视的键被其他客户端修改，重新尝试
                continue

-- MySQL更新语句示例
UPDATE products SET stock = stock - 1, version = version + 1 WHERE id = 123 AND version = 1;