# Not able to alter the table using pt-osc **URL:** \ **Category:** Percona Server for MySQL 8.0\ **Created:** [May 25, 2021, 8:55am UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589 "2021-05-25T08:55:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![robingaur](https://avatars.discourse-cdn.com/v4/letter/r/e56c9b/32.png) [@robingaur](https://forums.percona.com/u/robingaur)\ **Post date:** [May 25, 2021, 8:55am UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589/1 "2021-05-25T08:55:55Z")
I have a Mysql percona cluster with 2 nodes and 1 arbitrator node. I am trying to drop a column from the table using pt-online-schema-change using below command: ``` pt-online-schema-change u=root,p=xxx,D=database,t=table01 --alter="DROP COLUMN new_col" ``` But I’m getting the following error on running the command ``` Can't use an undefined value as an ARRAY reference at /usr/bin/pt-online-schema-change line 7684. ``` I’m new to pxc. I don’t know if the problem is in command or pxc configs. Table details: > CREATE TABLE `table01` ( > `id` bigint NOT NULL AUTO\_INCREMENT, > `username` varchar(128) NOT NULL, > `uuid` varchar(64) NOT NULL, > `randomString1` text NOT NULL, > `randomString2` varchar(64) NOT NULL, > `randomInt` int NOT NULL, > `status` varchar(10) NOT NULL, > `createdDate` datetime NOT NULL, > `updatedDate` datetime NOT NULL, > `new_col` varchar(128) NOT NULL DEFAULT ‘Test’, > PRIMARY KEY (`id`), > UNIQUE KEY `uuid_UNIQUE` (`uuid`), > KEY `username_INDEX` (`username`), > KEY `random_INDEX` (`randomString2`,`randomInt`) > ) ENGINE=InnoDB AUTO\_INCREMENT=12 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4\_0900\_ai\_ci ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [May 25, 2021, 1:05pm UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589/2 "2021-05-25T13:05:01Z")
Hi @robingaur, This error has absolutely nothing to do with your PXC configuration. This looks like a bug in the pt-osc software. Your table and the osc command look perfectly normal so that’s why this appears to be a bug. I recommend you file a bug report at [https://jira.percona.com/](https://jira.percona.com/) for the Percona Toolkit. How big is this table? Would a normal alter be a workaround for now? ---
**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\ **Post date:** [May 25, 2021, 1:08pm UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589/3 "2021-05-25T13:08:40Z")
Hi @robingaur, I created your table and ran pt-osc as you have shown and it worked for me. ``` [root@mysql1-T1 ~]# pt-online-schema-change D=sysbench,t=table01 --alter="DROP COLUMN new_col" --execute No slaves found. See --recursion-method if host mysql1-T1 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, 1 Altering `sysbench`.`table01`... Creating new table... Created new table sysbench._table01_new OK. Altering new table... Altered `sysbench`.`_table01_new` OK. 2021-05-25T13:07:16 Creating triggers... 2021-05-25T13:07:16 Created triggers OK. 2021-05-25T13:07:16 Copying approximately 1 rows... 2021-05-25T13:07:16 Copied rows OK. 2021-05-25T13:07:16 Analyzing new table... 2021-05-25T13:07:16 Swapping tables... 2021-05-25T13:07:16 Swapped original and new tables OK. 2021-05-25T13:07:16 Dropping old table... 2021-05-25T13:07:16 Dropped old table `sysbench`.`_table01_old` OK. 2021-05-25T13:07:16 Dropping triggers... 2021-05-25T13:07:16 Dropped triggers OK. Successfully altered `sysbench`.`table01`. ``` I’m using PXC 8.0.22 and Percona Toolkit 3.3.1. ---
**Author:** ![carlos.salguero](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/carlos.salguero/32/20_2.png) [@carlos.salguero](https://forums.percona.com/u/carlos.salguero)\ **Post date:** [May 25, 2021, 1:24pm UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589/4 "2021-05-25T13:24:07Z")
Hello. Could you try with `--no-version-check` and if that doesn’t work, run pt-online-schema-change again putting `PTDEBUG=1` before the command to enable debug mode. Thanks ---
**Author:** ![robingaur](https://avatars.discourse-cdn.com/v4/letter/r/e56c9b/32.png) [@robingaur](https://forums.percona.com/u/robingaur)\ **Post date:** [May 26, 2021, 10:37am UTC](https://forums.percona.com/t/not-able-to-alter-the-table-using-pt-osc/10589/5 "2021-05-26T10:37:27Z")
Hello @matthewb , I have 2 nodes with the same configs. On node 2, it is working fine but on node 1, it is failing with the above error. (`Can't use an undefined value as an ARRAY reference at /usr/bin/pt-online-schema-change line 7684.`) Hello @carlos.salguero, The above error is resolved after adding `--no-version-check`. After enabling debug mode, I find out the exact reason > VersionCheck:7681 60202 Version check failed: Cannot open /tmp/percona-version-check: Permission denied at /usr/bin/pt-online-schema-change line 7719. I don’t know if this is a bug or not as the same command is working in 1 node and not working in another. PS: Both the nodes have configuration/installation (installed using AMI).