Trouble running toolkit on live table


I’m trying to use percona toolkit to do a schema change on an active live table, and I’m having trouble at the creating triggers stage.

I’m running (something like)

pt-online-schema-change --max-lag 100000 --execute --alter “column_name int” t=table

the output gets as far as

2017-10-11T09:33:40 Creating triggers…

At this point it hangs (seemingly indefinitely but I gave it about 5 minutes). Meanwhile I can see a load of the following queuing up on the database:

Waiting for table metadata lock │ select count(*) from table where unique_id=‘Wd3XjrBiaQ4wi2CC7lq@uAAAAAY-16842’
I’ve no idea what to do, so any help would be appreciated!



Could you share some environmental information like OS, MySQL version and Toolkit version and, if it is possible, the output for SHOW CREATE TABLE for that table?


Thanks for the reply. This is RedHat EL6 running Maria DB 10.0.30, toolkit version 2.20.

Show create table is like this (some stuff changed / removed due to corporate sensitivity)

┃ Table ┃ Create Table ┃
│ name │ CREATE TABLE name ( │
│ │ id int(10) unsigned NOT NULL AUTO_INCREMENT, │
│ │ date datetime DEFAULT NULL, │
│ │ PRIMARY KEY (id), │
│ │ KEY column-x (column_x), │ │


Hi again,
In your post there is a key on column_x but column_x is not in the fields list and the alter is invalid.
I don’t know how to reproduce the issue.