MySQL 5.6使用pt-online-schema-change在线修改大表字段长度

业务需求： 在线修改一张2000W行表的字段长度。[root@21db01 ~]# pt-online-schema-change --alter="modify id  VARCHAR(64) CHARSET utf8 COLLATE utf8_general_ci   NOT NULL DEFAULT '0'  COMMENT 'ID';"  --user=root  --password=XXXX --host='127.0.0.1' D=users,t=users_dt  --charset=utf8 --execute --no-check-alter --no-check-replication-filtersCannot connect to A=utf8,D=users,h=10.1.4.80,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.4.82,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.6.7,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.4.97,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.6.8,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.4.81,p=...,u=rootCannot connect to A=utf8,D=users,h=10.1.4.79,p=...,u=rootNo slaves found.  See --recursion-method if host 21db01 has slaves.Not checking slave lag because no slaves were found and --check-slave-lag was not specified.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, 1Altering `users`.`users_dt`...Creating new table...Created new table users._users_dt_new OK.Altering new table...Altered `users`.`_users_dt_new` OK.2020-09-21T14:17:27 Creating triggers...2020-09-21T14:17:27 Created triggers OK.2020-09-21T14:17:27 Copying approximately 26345605 rows...Copying `users`.`users_dt`:   0% 01:12:38 remainCopying `users`.`users_dt`:   1% 01:13:24 remainCopying `users`.`users_dt`:   1% 01:20:53 remainCopying `users`.`users_dt`:   2% 01:27:24 remainCopying `users`.`users_dt`:   2% 01:31:22 remainCopying `users`.`users_dt`:   3% 01:32:27 remainCopying `users`.`users_dt`:  10% 01:58:39 remainCopying `users`.`users_dt`:  10% 01:58:30 remainCopying `users`.`users_dt`:  10% 01:59:12 remainCopying `users`.`users_dt`:  46% 01:20:35 remainCopying `users`.`users_dt`:  46% 01:20:22 remainCopying `users`.`users_dt`:  83% 24:06 remainCopying `users`.`users_dt`:  98% 01:23 remainCopying `users`.`users_dt`:  99% 00:37 remainCopying `users`.`users_dt`:  99% 00:03 remain2020-09-21T16:49:13 Copied rows OK.2020-09-21T16:49:13 Analyzing new table...2020-09-21T16:49:13 Swapping tables...2020-09-21T16:49:13 Swapped original and new tables OK.2020-09-21T16:49:13 Dropping old table...2020-09-21T16:49:50 Dropped old table `users`.`_users_dt_old` OK.2020-09-21T16:49:50 Dropping triggers...2020-09-21T16:49:50 Dropped triggers OK.Successfully altered `users`.`users_dt`. 总共耗时2小时多，普通磁盘。