MySQL千万级数据从190秒优化到1秒全过程

CREATE TABLE `orders` (
  `order_id` int NOT NULL AUTO_INCREMENT,
  `user_id` int DEFAULT NULL,
  `order_date` date NOT NULL,
  `total_amount` decimal(10,2) NOT NULL,
  PRIMARY KEY (`order_id`),
  KEY `idx_user_id` (`user_id`) USING BTREE,
  KEY `idx_user_amount` (`user_id`,`total_amount`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;

CREATE TABLE `users` (
  `user_id` int NOT NULL AUTO_INCREMENT,
  `username` varchar(50) COLLATE utf8mb4_general_ci NOT NULL,
  `email` varchar(100) COLLATE utf8mb4_general_ci NOT NULL,
  `created_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`user_id`),
  KEY `idx_user_id` (`user_id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;

-- 产生用户存储过程，1000个
CREATE DEFINER=`root`@`localhost` PROCEDURE `create_users`()
BEGIN
    DECLARE i INT DEFAULT 0;
    DECLARE total_users INT DEFAULT 1000; -- 调整用户数量
    DECLARE rnd_username VARCHAR(50);
    DECLARE rnd_email VARCHAR(100);

    WHILE i < total_users DO
        -- 生成随机用户名和邮箱
        SET rnd_username = CONCAT('User', FLOOR(1 + RAND() * 10000000)); -- 假设用户名唯一
        SET rnd_email = CONCAT(rnd_username, '@example.com'); -- 假设邮箱唯一
        -- 将数据插入用户表
        INSERT INTO users (username, email) VALUES (rnd_username, rnd_email);

        SET i = i + 1;
    END WHILE;
END

CREATE DEFINER=`root`@`localhost` PROCEDURE `generate_orders`()
BEGIN
    DECLARE i INT DEFAULT 0;
    DECLARE total_users INT DEFAULT 1000; -- 用户数量
    DECLARE total_orders_per_user INT DEFAULT 1000; -- 每个用户的订单数量
    DECLARE rnd_user_id INT;
    DECLARE rnd_order_date DATE;
    DECLARE rnd_total_amount DECIMAL(10, 2);
    DECLARE j INT DEFAULT 0;

    WHILE i < total_users DO
        -- 获取用户ID
        SELECT user_id INTO rnd_user_id FROM users LIMIT i, 1;

        WHILE j < total_orders_per_user DO
            -- 生成订单日期和总金额
            SET rnd_order_date = DATE_ADD('2020-01-01', INTERVAL FLOOR(RAND() * 1096) DAY); -- 2020-01-01和2022-12-31之间的随机日期
            SET rnd_total_amount = ROUND(RAND() * 1000, 2); -- 0到1000之间的随机总金额
            -- 将数据插入订单表
            INSERT INTO orders (user_id, order_date, total_amount) VALUES (rnd_user_id, rnd_order_date, rnd_total_amount);

            SET j = j + 1;
        END WHILE;
        SET j = 0;

        SET i = i + 1;
    END WHILE;
END

-- 第一个版本
SELECT a.*,sum(b.total_amount) as total from users a left join orders b  on a.user_id = b.user_id
group by a.user_id;

CREATE INDEX idx_orders_user_id ON orders (user_id);
CREATE INDEX idx_orders_total_amount ON orders (total_amount);
CREATE INDEX idx_users_user_id ON users (user_id);

-- 第一个版本
SELECT a.*,sum(b.total_amount) as total from users a left join orders b  on a.user_id = b.user_id
group by a.user_id;

-- 先不删除普通索引
-- drop INDEX idx_orders_user_id ON orders;
-- drop INDEX idx_orders_total_amount ON orders;
CREATE INDEX idx_orders_total_amount_user_id ON orders (total_amount,user_id);
CREATE INDEX idx_orders_user_id_total_amount ON orders (user_id,total_amount);

-- 第一个版本
SELECT a.*,sum(b.total_amount) as total from users a left join orders b  on a.user_id = b.user_id
group by a.user_id;

from
on
join
where
group by
having
select
distinct
union （all）
order by
limit

drop INDEX idx_orders_user_id ON orders;
drop INDEX idx_orders_total_amount ON orders;
drop INDEX idx_orders_total_amount_user_id ON orders;

-- 第三次优化：减少数据量
SELECT a.*,sum(b.total_amount) as total from users a left join orders b  on a.user_id = b.user_id
where a.user_id > 1033
group by a.user_id;

-- 第三个版本，小标驱动大表  没啥效果
SELECT a.*,sum(b.total_amount) as total from users a
left join (select user_id,total_amount from orders c where c.user_id > 1033 ) b  on a.user_id = b.user_id
where a.user_id > 1033
group by a.user_id;

-- 第五个版本，强制索引 
SELECT a.*,sum(b.total_amount) as total from users a left join orders b force index (idx_orders_user_id_total_amount)  on a.user_id = b.user_id
where b.user_id in (1033,1034,1035,1036,1037,1038)
group by a.user_id;
-- 第五个版本，不走强制索引 
SELECT a.*,sum(b.total_amount) as total from users a left join orders b  on a.user_id = b.user_id
where b.user_id in (1033,1034,1035,1036,1037,1038)
group by a.user_id;