MySQL 5.7使用pt-online-schema-change對大表加欄位

業務需求：

對一張線上的3000W行的表加欄位：

用普通方式，建議小表使用：

ALTER TABLE `idempotent`

ADD COLUMN `orderid` VARCHAR(20) NULL DEFAULT NULL COMMENT '業務單據號' AFTER `isdelete`;

ALTER TABLE ship_type ADD printer_name VARCHAR(50)  COMMENT '印表機名稱';

大表會鎖表。

對大表加欄位，建議用pt-online-schema-change工具，可以不鎖表。

對錶 idempotent加欄位 orderid：

命令：

[root@DB001 ~]#pt-online-schema-change --user=root --password=123456 --host=192.168.1.18  --alter "ADD COLUMN orderid VARCHAR(20) NULL DEFAULT NULL COMMENT '業務單據號'" D=ora,t=idempotent --no-check-replication-filters  --execute

Found 1 slaves:

localhost.localdomain -> 192.168.1.19:socket

Will check slave lag on:

localhost.localdomain -> 192.168.1.19:socket

Operation, tries, wait:

  analyze_table, 10, 1

  copy_rows, 10, 0.25

  create_triggers, 10, 1

  drop_triggers, 10, 1

  swap_tables, 10, 1

  update_foreign_keys, 10, 1

Altering `ora`.`idempotent`...

Creating new table...

Created new table ora._idempotent_new OK.

Altering new table...

Altered `ora`.`_idempotent_new` OK.

2019-10-23T19:01:00 Creating triggers...

2019-10-23T19:01:00 Created triggers OK.

2019-10-23T19:01:00 Copying approximately 24968401 rows...

Copying `ora`.`idempotent`:   4% 10:53 remain

Copying `ora`.`idempotent`:   8% 10:40 remain

Copying `ora`.`idempotent`:  11% 11:49 remain

Copying `ora`.`idempotent`:  14% 12:08 remain

Copying `ora`.`idempotent`:  17% 12:09 remain

Copying `ora`.`idempotent`:  19% 12:15 remain

Copying `ora`.`idempotent`:  22% 12:15 remain

Copying `ora`.`idempotent`:  24% 12:11 remain

Copying `ora`.`idempotent`:  27% 12:09 remain

Copying `ora`.`idempotent`:  29% 12:03 remain

Copying `ora`.`idempotent`:  31% 11:45 remain

Copying `ora`.`idempotent`:  34% 11:23 remain

Copying `ora`.`idempotent`:  37% 11:01 remain

Copying `ora`.`idempotent`:  39% 10:39 remain

Copying `ora`.`idempotent`:  42% 10:11 remain

Copying `ora`.`idempotent`:  44% 09:50 remain

Copying `ora`.`idempotent`:  47% 09:35 remain

Copying `ora`.`idempotent`:  49% 09:14 remain

Copying `ora`.`idempotent`:  52% 08:44 remain

Copying `ora`.`idempotent`:  55% 08:10 remain

Copying `ora`.`idempotent`:  59% 07:17 remain

Copying `ora`.`idempotent`:  63% 06:21 remain

Copying `ora`.`idempotent`:  67% 05:32 remain

Copying `ora`.`idempotent`:  71% 04:44 remain

Copying `ora`.`idempotent`:  75% 03:59 remain

Copying `ora`.`idempotent`:  80% 03:11 remain

Copying `ora`.`idempotent`:  84% 02:28 remain

Copying `ora`.`idempotent`:  88% 01:49 remain

Copying `ora`.`idempotent`:  92% 01:08 remain

Copying `ora`.`idempotent`:  96% 00:28 remain

2019-10-23T19:18:24 Copied rows OK.

2019-10-23T19:18:24 Analyzing new table...

2019-10-23T19:18:24 Swapping tables...

2019-10-23T19:18:24 Swapped original and new tables OK.

2019-10-23T19:18:24 Dropping old table...

2019-10-23T19:18:26 Dropped old table `ora`.`_idempotent_old` OK.

2019-10-23T19:18:26 Dropping triggers...

2019-10-23T19:18:26 Dropped triggers OK.

Successfully altered `ora`.`idempotent`.

You have mail in /var/spool/mail/root

整個過程持續10幾分鐘，不鎖表。

欄位新增完成。

PS：

切記在業務低峰執行。

可以指定字符集，防止加好欄位的表的註釋出現亂碼。

修改註釋：

ALTER TABLE idempotent MODIFY COLUMN `sysno` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '編號';