Foreign key related issues are very common when dealing with DDL changes in MySQL using Percona toolkit. In this blog post, I will explain how the tool (pt-online-schema-change) handles foreign key constraints when executing a DDL change. First of all, I would like to explain why foreign keys have to be handled at all before [&]

https://www.percona.com/blog/2019/06/07/how-pt-online-schema-change-handles-foreign-keys/