业务需求：在线对MySQL 5.7的一个大表加索引。普通加索引方式，适合于小表： ALTER TABLE `EMP`ADD INDEX IDX_EMP_ORDERSYSNO (ORDERSYSNO) USING BTREE; 对大表需要使用pt-online-schema-change工具，可以不锁表。
加组合字段索引：
[root@DB02 ~]# pt-online-schema-change --user=root --password=123456 --host=192.168.1.18 --alter "ADD INDEX IDX_DOSTELLE_ST (SEGMENT,transaction) USING BTREE" D=ora,t=dostelle --no-check-replication-filters --execute --charset=utf8 --max-load=Threads_running=20 加单一字段索引：[root@DB001 ~]# pt-online-schema-change --user=root --password=XXX --host=192.168.1.98 --alter "ADD INDEX IDX_ORDERID (ORDERID) USING BTREE" D=ora,t=idemp --no-check-replication-filters --execute --charset=utf8 --max-load=Threads_running=20Found 1 slaves:localhost.localdomain -> 192.168.1.99:socketWill check slave lag on:localhost.localdomain -> 192.168.1.99:socketOperation, 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 `ora`.`idemp`...Creating new table...Created new table ora._idemp_new OK.Altering new table...Altered `ora`.`_idemp_new` OK.2021-02-01T11:33:58 Creating triggers...2021-02-01T11:34:40 Created triggers OK.2021-02-01T11:34:40 Copying approximately 6915514 rows...Copying `ora`.`idemp`: 11% 04:01 remainCopying `ora`.`idemp`: 20% 03:46 remainCopying `ora`.`idemp`: 31% 03:18 remainCopying `ora`.`idemp`: 41% 02:49 remainCopying `ora`.`idemp`: 50% 02:25 remainCopying `ora`.`idemp`: 60% 01:59 remainCopying `ora`.`idemp`: 70% 01:29 remainCopying `ora`.`idemp`: 80% 00:58 remainCopying `ora`.`idemp`: 90% 00:29 remainCopying `ora`.`idemp`: 99% 00:00 remain2021-02-01T11:50:59 Copied rows OK.2021-02-01T11:50:59 Analyzing new table...2021-02-01T11:50:59 Swapping tables...2021-02-01T11:51:13 Swapped original and new tables OK.2021-02-01T11:51:13 Dropping old table...2021-02-01T11:51:14 Dropped old table `ora`.`_idemp_old` OK.2021-02-01T11:51:14 Dropping triggers...2021-02-01T11:51:14 Dropped triggers OK.Successfully altered `ora`.`idemp`.You have mail in /var/spool/mail/root
