MySQL亿级大表安全添加字段的实战指南

ALTER TABLE `orders` ADD COLUMN `is_priority` TINYINT NULL DEFAULT 0;

-- 查看表大小（GB）
SELECT
    table_name,
    ROUND(data_length/1024/1024/1024,2) AS size_gb
FROM information_schema.tables
WHERE table_schema = 'your_db' AND table_name = 'orders';

-- 检查当前长事务
SELECT * FROM information_schema.innodb_trx
WHERE TIME_TO_SEC(TIMEDIFF(NOW(), trx_started)) > 60;

mysqldump -u [username] -p[password] [database_name] [table_name] > [backup_file_name].sql

ALTER TABLE `orders`
ADD COLUMN `is_priority` TINYINT NULL DEFAULT 0,
ALGORITHM=INPLACE,
LOCK=NONE;

SHOW PROCESSLIST;

SELECT * FROM information_schema.innodb_alter_table;

时间(分钟) = 表大小(GB) × 2 + 10

# 安装 Percona Toolkit
sudo yum install percona-toolkit

# 执行变更
pt-online-schema-change \
--alter "ADD COLUMN is_priority TINYINT NULL DEFAULT 0" \
D=your_db,t=orders \
--chunk-size=1000 \
--max-load="Threads_running=50" \
--critical-load="Threads_running=100" \
--execute

try {
    orderDao.insert(newOrder);
} catch (DuplicateKeyException e) {
    orderDao.update(newOrder);
}

gh-ost \
--database="your_db" \
--table="orders" \
--alter="ADD COLUMN is_priority TINYINT NULL DEFAULT 0" \
--assume-rbr \
--allow-on-master \
--cut-over=default \
--execute

public void createOrder(Order order) {
    order.setIsPriority(0); // 新字段默认值
    orderMapper.insert(order);

    // 兼容旧代码
    if (order.getV2() == null) {
        orderMapper.updateIsPriority(order.getId(), 0);
    }
}

<insert id="insertOrder">
    INSERT INTO orders
    (id, user_id, amount
    <if test="isPriority != null">, is_priority</if>)
    VALUES
    (#{id}, #{userId}, #{amount}
    <if test="isPriority != null">, #{isPriority}</if>)
</insert>

pt-heartbeat --monitor --database=your_db

tail -f gh-ost.log

pt-online-schema-change --drop-new-table --alter="..." --execute

gh-ost --panic-on-failure --revert

SELECT COUNT(*) FROM orders WHERE is_priority IS NULL;

ALTER TABLE orders
MODIFY COLUMN is_priority TINYINT NOT NULL DEFAULT 0;