Comment 5 for bug 1640164

Hmm, I think there was a foreign key drop in 015, I didn't mention above.

Anh, are you using Rolling schema updates as described here?
http://galeracluster.com/documentation-webpages/schemaupgrades.html

I don't know if that would fix your problem here, but it looks like it could help, if a bit fiddly. We do the odd table create, which may cause problems, by the looks of things.

It seems MariaDB doesn't support as much online DDL as MySQL 5.6 as described here:
https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-overview.html
Although even in that case we have some type changes that look like they would block a lot of online operations :(

I think we need quite a deep look again at this problem.