[viraptor]

Ok, one problem solved. Now what's left is - schema change, making sure ongoing process flows can automatically migrate from the previous version to the new one, resources referenced from the previous version are still valid, nothing tries to read files with the code via the link (it can change mid-request).

I got the strange feeling from that article as if changing the code files was the hardest thing about yes upgrade.

[ibotty]

you are certainly right. db schema updates are the hard part.

for db schema updates: have a look at sqitch by postgres' david wheeler. it should also support mysql (or will in the future).