Preface
As we all know,it's really a troublesome thing to DBA in scenario of changing table structure online.Since MySQL 5.6,it support online ddl operations.On the other hand,we also use third party tool such as gh-ost.Let's learn another famous tool of Percona-Toolkit,that is pt-online-schema-change.
Introduce
pt-osc is a tool which is commonly used in Percona-Toolkit suits which .It bases on triggers,by creating temporary middle table to dipose the table structure changing issue.MySQL 8.0.13 will support a new feature of instant adding columns(but only add,not change).Therefore,ps-osc still has its value in the "online ddl change" field.
Procedure
1 ###Commonly used parameter introduce.### 2 connect parameter: 3 -h hostname -P port -u username -p password -S socket 4 5 output parameter: 6 --print -- Show whole procedure of ddl operation on the screen. 7 8 main parameter: 9 --alter -- Specify the ddl statement using quotation mark behind. 10 11 alternative parameter: 12 --dry-run -- Only operate the new table instead of original one. 13 --execute -- Directly do all opertion both new and original table. 14 15 other parameter: 16 --no-check-alter -- Don't parse your ddl statment which follows behind. 17 --ask-pass -- You cannot use -p without a string to input password,so you need this parameter. 18 19 ###Create test table.### 20 (root@localhost mysql3306.sock)[zlm]09:38:11>create table test_ddl( 21 -> id int unsigned auto_increment, 22 -> name varchar(20) not null default '', 23 -> tel tinyint unsigned not null default 0, 24 -> primary key(id) 25 -> ) engine=innodb charset=utf8mb4; 26 Query OK, 0 rows affected (0.01 sec) 27 28 ###Insert records into table.### 29 (root@localhost mysql3306.sock)[zlm]09:39:28>insert into test_ddl(name,tel) values('zlm',13866668888); 30 ERROR 1264 (22003): Out of range value for column 'tel' at row 1 31 (root@localhost mysql3306.sock)[zlm]09:41:07>insert into test_ddl(name,tel) values('zlm',256); 32 ERROR 1264 (22003): Out of range value for column 'tel' at row 1 33 (root@localhost mysql3306.sock)[zlm]09:41:18>insert into test_ddl(name,tel) values('zlm',255); -- Scope of unsigned tinyint is 0~255. 34 Query OK, 1 row affected (0.00 sec) 35 36 (root@localhost mysql3306.sock)[zlm]09:41:22>select * from test_ddl; 37 +----+------+-----+ 38 | id | name | tel | 39 +----+------+-----+ 40 | 11 | zlm | 255 | 41 +----+------+-----+ 42 1 row in set (0.00 sec) 43 44 ###Change column "tel" from tinyint to bigint.### 45 [root@zlm2 09:52:25 ~] 46 #pt-online-schema-change -hzlm2 -P3306 -uroot --ask-pass --alter "modify tel bigint default 0" --print --execute --no-check-alter D=zlm,t=test_ddl 47 Enter MySQL password: 48 49 ###Check slave information.### 50 No slaves found. See --recursion-method if host zlm2 has slaves. 51 Not checking slave lag because no slaves were found and --check-slave-lag was not specified. 52 53 ###Summary of operations.### 54 Operation, tries, wait: 55 analyze_table, 10, 1 56 copy_rows, 10, 0.25 57 create_triggers, 10, 1 58 drop_triggers, 10, 1 59 swap_tables, 10, 1 60 update_foreign_keys, 10, 1 61 Altering `zlm`.`test_ddl`... 62 63 ###Create new table.### 64 Creating new table... 65 CREATE TABLE `zlm`.`_test_ddl_new` ( 66 `id` int(10) unsigned NOT NULL AUTO_INCREMENT, 67 `name` varchar(20) NOT NULL DEFAULT '', 68 `tel` tinyint(3) unsigned NOT NULL DEFAULT '0', 69 PRIMARY KEY (`id`) 70 ) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 71 Created new table zlm._test_ddl_new OK. 72 73 ###Alter column in new table.### 74 Altering new table... 75 ALTER TABLE `zlm`.`_test_ddl_new` modify tel bigint default 0 76 Altered `zlm`.`_test_ddl_new` OK. -- If you specify "dry-run",it will end here. 77 78 ###Create Triggers.### 79 2018-06-20T10:38:43 Creating triggers... 80 2018-06-20T10:38:43 Created triggers OK. 81 82 ###Copy rows into new table.### 83 2018-06-20T10:38:43 Copying approximately 1 rows... 84 INSERT LOW_PRIORITY IGNORE INTO `zlm`.`_test_ddl_new` (`id`, `name`, `tel`) SELECT `id`, `name`, `tel` FROM `zlm`.`test_ddl` LOCK IN SHARE MODE /*pt-online-schema-change 4190 copy table*/ 85 2018-06-20T10:38:43 Copied rows OK. 86 87 ###Swap oraiginal table with new table.### 88 2018-06-20T10:38:43 Analyzing new table... 89 2018-06-20T10:38:43 Swapping tables... 90 RENAME TABLE `zlm`.`test_ddl` TO `zlm`.`_test_ddl_old`, `zlm`.`_test_ddl_new` TO `zlm`.`test_ddl` 91 2018-06-20T10:38:43 Swapped original and new tables OK. 92 93 ###Drop original table.### 94 2018-06-20T10:38:43 Dropping old table... 95 DROP TABLE IF EXISTS `zlm`.`_test_ddl_old` 96 2018-06-20T10:38:43 Dropped old table `zlm`.`_test_ddl_old` OK. 97 98 ###Drop triggers.### 99 2018-06-20T10:38:43 Dropping triggers... 100 DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_del` 101 DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_upd` 102 DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_ins` 103 2018-06-20T10:38:43 Dropped triggers OK. 104 Successfully altered `zlm`.`test_ddl`. 105 106 ###Check table ddl.### 107 (root@localhost mysql3306.sock)[zlm]09:58:32>show create table test_ddl; 108 +----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 109 | Table | Create Table | 110 +----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 111 | test_ddl | CREATE TABLE `test_ddl` ( 112 `id` int(10) unsigned NOT NULL AUTO_INCREMENT, 113 `name` varchar(20) NOT NULL DEFAULT '', 114 `tel` bigint(20) DEFAULT '0', -- The column "tel" has be changed into bigint type now. 115 PRIMARY KEY (`id`) 116 ) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 | 117 +----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 118 1 row in set (0.01 sec) 119 120 ###Check general log file for detail.### 121 [root@zlm2 10:38:54 /data/mysql/mysql3306/data] 122 #cat zlm2.log 123 124 mysqld, Version: 5.7.21-log (MySQL Community Server (GPL)). started with: 125 Tcp port: 3306 Unix socket: /tmp/mysql3306.sock 126 Time Id Command Argument 127 2018-06-20T08:38:37.476403Z 16 Query show global variables like '%general_log%' 128 2018-06-20T08:38:43.828985Z 19 Connect root@localhost on zlm using TCP/IP 129 2018-06-20T08:38:43.829297Z 19 Query SHOW VARIABLES LIKE 'innodb\_lock_wait_timeout' 130 2018-06-20T08:38:43.832850Z 19 Query SET SESSION innodb_lock_wait_timeout=1 131 2018-06-20T08:38:43.833041Z 19 Query SHOW VARIABLES LIKE 'lock\_wait_timeout' 132 2018-06-20T08:38:43.836907Z 19 Query SET SESSION lock_wait_timeout=60 133 2018-06-20T08:38:43.837752Z 19 Query SHOW VARIABLES LIKE 'wait\_timeout' 134 2018-06-20T08:38:43.842090Z 19 Query SET SESSION wait_timeout=10000 135 2018-06-20T08:38:43.842222Z 19 Query SELECT @@SQL_MODE 136 2018-06-20T08:38:43.842350Z 19 Query SET @@SQL_QUOTE_SHOW_CREATE = 1/*!40101, @@SQL_MODE='NO_AUTO_VALUE_ON_ZERO,ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'*/ 137 2018-06-20T08:38:43.842453Z 19 Query SELECT @@server_id /*!50038 , @@hostname*/ 138 2018-06-20T08:38:43.843311Z 20 Connect root@localhost on zlm using TCP/IP 139 2018-06-20T08:38:43.843620Z 20 Query SHOW VARIABLES LIKE 'innodb\_lock_wait_timeout' 140 2018-06-20T08:38:43.847069Z 20 Query SET SESSION innodb_lock_wait_timeout=1 141 2018-06-20T08:38:43.847442Z 20 Query SHOW VARIABLES LIKE 'lock\_wait_timeout' 142 2018-06-20T08:38:43.851645Z 20 Query SET SESSION lock_wait_timeout=60 143 2018-06-20T08:38:43.851904Z 20 Query SHOW VARIABLES LIKE 'wait\_timeout' 144 2018-06-20T08:38:43.853942Z 20 Query SET SESSION wait_timeout=10000 145 2018-06-20T08:38:43.854029Z 20 Query SELECT @@SQL_MODE 146 2018-06-20T08:38:43.854055Z 20 Query SET @@SQL_QUOTE_SHOW_CREATE = 1/*!40101, @@SQL_MODE='NO_AUTO_VALUE_ON_ZERO,ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'*/ 147 2018-06-20T08:38:43.854152Z 20 Query SELECT @@server_id /*!50038 , @@hostname*/ 148 2018-06-20T08:38:43.854356Z 19 Query SHOW VARIABLES LIKE 'wsrep_on' 149 2018-06-20T08:38:43.857148Z 19 Query SHOW VARIABLES LIKE 'version%' 150 2018-06-20T08:38:43.860325Z 19 Query SHOW ENGINES 151 2018-06-20T08:38:43.861002Z 19 Query SHOW VARIABLES LIKE 'innodb_version' 152 2018-06-20T08:38:43.864957Z 19 Query SHOW VARIABLES LIKE 'innodb_stats_persistent' 153 2018-06-20T08:38:43.867873Z 19 Query SELECT @@SERVER_ID 154 2018-06-20T08:38:43.868114Z 19 Query SHOW GRANTS FOR CURRENT_USER() 155 2018-06-20T08:38:43.868774Z 19 Query SHOW FULL PROCESSLIST 156 2018-06-20T08:38:43.869245Z 19 Query SHOW SLAVE HOSTS 157 2018-06-20T08:38:43.869849Z 19 Query SHOW GLOBAL STATUS LIKE 'Threads_running' 158 2018-06-20T08:38:43.874152Z 19 Query SHOW GLOBAL STATUS LIKE 'Threads_running' 159 2018-06-20T08:38:43.877509Z 19 Query SELECT CONCAT(@@hostname, @@port) 160 2018-06-20T08:38:43.877973Z 19 Query SHOW TABLES FROM `zlm` LIKE 'test\_ddl' 161 2018-06-20T08:38:43.878229Z 19 Query SELECT VERSION() 162 2018-06-20T08:38:43.879011Z 19 Query SHOW TRIGGERS FROM `zlm` LIKE 'test\_ddl' 163 2018-06-20T08:38:43.879506Z 19 Query /*!40101 SET @OLD_SQL_MODE := @@SQL_MODE, @@SQL_MODE := '', @OLD_QUOTE := @@SQL_QUOTE_SHOW_CREATE, @@SQL_QUOTE_SHOW_CREATE := 1 */ 164 2018-06-20T08:38:43.879602Z 19 Query USE `zlm` 165 2018-06-20T08:38:43.879706Z 19 Query SHOW CREATE TABLE `zlm`.`test_ddl` 166 2018-06-20T08:38:43.880123Z 19 Query /*!40101 SET @@SQL_MODE := @OLD_SQL_MODE, @@SQL_QUOTE_SHOW_CREATE := @OLD_QUOTE */ 167 2018-06-20T08:38:43.880979Z 19 Query EXPLAIN SELECT * FROM `zlm`.`test_ddl` WHERE 1=1 168 2018-06-20T08:38:43.881846Z 19 Query SELECT table_schema, table_name FROM information_schema.key_column_usage WHERE referenced_table_schema='zlm' AND referenced_table_name='test_ddl' 169 2018-06-20T08:38:43.893011Z 19 Query /*!40101 SET @OLD_SQL_MODE := @@SQL_MODE, @@SQL_MODE := '', @OLD_QUOTE := @@SQL_QUOTE_SHOW_CREATE, @@SQL_QUOTE_SHOW_CREATE := 1 */ 170 2018-06-20T08:38:43.893622Z 19 Query USE `zlm` 171 2018-06-20T08:38:43.893798Z 19 Query SHOW CREATE TABLE `zlm`.`test_ddl` 172 2018-06-20T08:38:43.893954Z 19 Query /*!40101 SET @@SQL_MODE := @OLD_SQL_MODE, @@SQL_QUOTE_SHOW_CREATE := @OLD_QUOTE */ 173 2018-06-20T08:38:43.894730Z 19 Query CREATE TABLE `zlm`.`_test_ddl_new` ( 174 `id` int(10) unsigned NOT NULL AUTO_INCREMENT, 175 `name` varchar(20) NOT NULL DEFAULT '', 176 `tel` int(11) DEFAULT '0', 177 PRIMARY KEY (`id`) 178 ) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 179 2018-06-20T08:38:43.914358Z 19 Query ALTER TABLE `zlm`.`_test_ddl_new` modify tel bigint default 0 180 2018-06-20T08:38:43.934771Z 19 Query /*!40101 SET @OLD_SQL_MODE := @@SQL_MODE, @@SQL_MODE := '', @OLD_QUOTE := @@SQL_QUOTE_SHOW_CREATE, @@SQL_QUOTE_SHOW_CREATE := 1 */ 181 2018-06-20T08:38:43.934930Z 19 Query USE `zlm` 182 2018-06-20T08:38:43.935044Z 19 Query SHOW CREATE TABLE `zlm`.`_test_ddl_new` 183 2018-06-20T08:38:43.936057Z 19 Query /*!40101 SET @@SQL_MODE := @OLD_SQL_MODE, @@SQL_QUOTE_SHOW_CREATE := @OLD_QUOTE */ 184 2018-06-20T08:38:43.936926Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'DELETE' AND ACTION_TIMING = 'AFTER' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 185 2018-06-20T08:38:43.937687Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'UPDATE' AND ACTION_TIMING = 'AFTER' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 186 2018-06-20T08:38:43.939328Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'INSERT' AND ACTION_TIMING = 'AFTER' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 187 2018-06-20T08:38:43.940991Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'DELETE' AND ACTION_TIMING = 'BEFORE' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 188 2018-06-20T08:38:43.942390Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'UPDATE' AND ACTION_TIMING = 'BEFORE' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 189 2018-06-20T08:38:43.943844Z 19 Query SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_MANIPULATION = 'INSERT' AND ACTION_TIMING = 'BEFORE' AND TRIGGER_SCHEMA = 'zlm' AND EVENT_OBJECT_TABLE = 'test_ddl' 190 2018-06-20T08:38:43.944624Z 19 Query CREATE TRIGGER `pt_osc_zlm_test_ddl_del` AFTER DELETE ON `zlm`.`test_ddl` FOR EACH ROW DELETE IGNORE FROM `zlm`.`_test_ddl_new` WHERE `zlm`.`_test_ddl_new`.`id` <=> OLD.`id` 191 2018-06-20T08:38:43.949413Z 19 Query CREATE TRIGGER `pt_osc_zlm_test_ddl_upd` AFTER UPDATE ON `zlm`.`test_ddl` FOR EACH ROW BEGIN DELETE IGNORE FROM `zlm`.`_test_ddl_new` WHERE !(OLD.`id` <=> NEW.`id`) AND `zlm`.`_test_ddl_new`.`id` <=> OLD.`id`;REPLACE INTO `zlm`.`_test_ddl_new` (`id`, `name`, `tel`) VALUES (NEW.`id`, NEW.`name`, NEW.`tel`);END 192 2018-06-20T08:38:43.954329Z 19 Query CREATE TRIGGER `pt_osc_zlm_test_ddl_ins` AFTER INSERT ON `zlm`.`test_ddl` FOR EACH ROW REPLACE INTO `zlm`.`_test_ddl_new` (`id`, `name`, `tel`) VALUES (NEW.`id`, NEW.`name`, NEW.`tel`) 193 2018-06-20T08:38:43.959241Z 19 Query EXPLAIN SELECT * FROM `zlm`.`test_ddl` WHERE 1=1 194 2018-06-20T08:38:43.961358Z 19 Query EXPLAIN SELECT `id`, `name`, `tel` FROM `zlm`.`test_ddl` LOCK IN SHARE MODE /*explain pt-online-schema-change 4190 copy table*/ 195 2018-06-20T08:38:43.962004Z 19 Query INSERT LOW_PRIORITY IGNORE INTO `zlm`.`_test_ddl_new` (`id`, `name`, `tel`) SELECT `id`, `name`, `tel` FROM `zlm`.`test_ddl` LOCK IN SHARE MODE /*pt-online-schema-change 4190 copy table*/ 196 2018-06-20T08:38:43.962769Z 19 Query SHOW WARNINGS 197 2018-06-20T08:38:43.963561Z 19 Query SHOW GLOBAL STATUS LIKE 'Threads_running' 198 2018-06-20T08:38:43.966643Z 19 Query ANALYZE TABLE `zlm`.`_test_ddl_new` /* pt-online-schema-change */ 199 2018-06-20T08:38:43.968221Z 19 Query RENAME TABLE `zlm`.`test_ddl` TO `zlm`.`_test_ddl_old`, `zlm`.`_test_ddl_new` TO `zlm`.`test_ddl` 200 2018-06-20T08:38:43.983005Z 19 Query DROP TABLE IF EXISTS `zlm`.`_test_ddl_old` 201 2018-06-20T08:38:43.990393Z 19 Query DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_del` 202 2018-06-20T08:38:43.991005Z 19 Query DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_upd` 203 2018-06-20T08:38:43.991346Z 19 Query DROP TRIGGER IF EXISTS `zlm`.`pt_osc_zlm_test_ddl_ins` 204 2018-06-20T08:38:43.991966Z 19 Query SHOW TABLES FROM `zlm` LIKE '\_test\_ddl\_new' 205 2018-06-20T08:38:43.999016Z 20 Quit 206 2018-06-20T08:38:44.000302Z 19 Quit
Supplement
1 ###Create a test table "test_ddl_no_pk" without primary key.### 2 (root@localhost mysql3306.sock)[zlm]04:17:53>create table test_ddl_no_pk( 3 -> id int unsigned, 4 -> name varchar(20) not null default '', 5 -> tel tinyint unsigned not null default 0 6 -> ) engine=innodb charset=utf8mb4; 7 Query OK, 0 rows affected (0.12 sec) 8 9 (root@localhost mysql3306.sock)[zlm]04:18:11>insert into test_ddl_no_pk(id,name,tel) values(1,'zlm','110'),(2,'aaron8219','119'); 10 Query OK, 2 rows affected (0.00 sec) 11 Records: 2 Duplicates: 0 Warnings: 0 12 13 ###Insert two records into above table.### 14 (root@localhost mysql3306.sock)[zlm]04:18:26>select * from test_ddl_no_pk; 15 +------+-----------+-----+ 16 | id | name | tel | 17 +------+-----------+-----+ 18 | 1 | zlm | 110 | 19 | 2 | aaron8219 | 119 | 20 +------+-----------+-----+ 21 2 rows in set (0.00 sec) 22 23 ###Execute pt-osc again.### 24 [root@zlm2 04:14:14 ~] 25 #pt-online-schema-change -hzlm2 -P3306 -uroot --ask-pass --alter "modify tel bigint default 0" --print --execute --no-check-alter D=zlm,t=test_ddl_no_pk 26 Enter MySQL password: 27 No slaves found. See --recursion-method if host zlm2 has slaves. 28 Not checking slave lag because no slaves were found and --check-slave-lag was not specified. 29 Operation, tries, wait: 30 analyze_table, 10, 1 31 copy_rows, 10, 0.25 32 create_triggers, 10, 1 33 drop_triggers, 10, 1 34 swap_tables, 10, 1 35 update_foreign_keys, 10, 1 36 Altering `zlm`.`test_ddl_no_pk`... 37 Creating new table... 38 CREATE TABLE `zlm`.`_test_ddl_no_pk_new` ( 39 `id` int(10) unsigned DEFAULT NULL, 40 `name` varchar(20) NOT NULL DEFAULT '', 41 `tel` tinyint(3) unsigned NOT NULL DEFAULT '0' 42 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 43 Created new table zlm._test_ddl_no_pk_new OK. 44 Altering new table... 45 ALTER TABLE `zlm`.`_test_ddl_no_pk_new` modify tel bigint default 0 46 Altered `zlm`.`_test_ddl_no_pk_new` OK. 47 2018-06-21T04:19:42 Dropping new table... 48 DROP TABLE IF EXISTS `zlm`.`_test_ddl_no_pk_new`; -- There're no create triggers,copy rows and swap table operations any more but directly drop new table operation. 49 2018-06-21T04:19:42 Dropped new table OK. 50 `zlm`.`test_ddl_no_pk` was not altered. 51 The new table `zlm`.`_test_ddl_no_pk_new` does not have a PRIMARY KEY or a unique index which is required for the DELETE trigger. -- Indicate the reason why it stop working.
Summary
- pt-ocs depends on tirggers,there mustn't be triggers on original table.
- Primary key or unique key is indispensable when use it.Otherwise,it won't work normally.
- Although pt-ocs won't block online transactions but still recommend do online ddl operations in off-peak period.