pt-online-schema-change replication support idea

[Michaël de Groot]

Hi,

I'm not too good at perl myself, but I have an idea to make pt-online-schema-change support row based replication; it's quite easy.

There ar, as far as I have noticed, 2 problems when running pt-online-schema-change in replication:
1. Master performance may differ from slave performance, therefor you cannot just replicate it
2. osc cannot influence binlog state from within a trigger

My idea is this:
Instead of just locally creating the temp table, first create a BLACKHOLE table with sql_log_bin=1. Then, after setting sql_log_bin=0, alter the tmp table to the correct engine.

1 problem arises: You still cannot alter table on both the slaves and the master at the same time. To fix this, you should put (for example) the MySQL server id of the current server in the generated tmp table name.

If my perl skills were better I would have implemented it. :)

Thanks

[Daniel Nichter (daniel-nichter)]

Thanks for this idea. Since this is not a bug but a feature, I've created https://blueprints.launchpad.net/percona-toolkit/+spec/rbr-support-for-pt-osc for you in case you want to implement this in a branch.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-911