Recently I faced the problem that my Db became very huge and I cannot allow to myself downtime every time when I want to change the schema.
This caused me to start looking for solution that do schema changing online.
1) pt-online-schema-change. Very attractive project, but honestly I was disappointed. Having downloaded the newest version, I had to change the code in order to get the script working. At the beggining script fails with error messages. All of them I found on the bug report of Percona. After patching script did it's job, hopefully well.
If you are more experienced, please share with us your opinion. What's the best and most reliable product?