Dear developers from roundcube,

I'm a student at the University of Applied Sciences in Regensburg (Germany).
Currently I'm working on my master's thesis, contributing to a research project in the field quantitative software engineering. 
By mining the software histories of popular open source projects, we want to get insight about current development practices and challenges.
Our main focus here is to understand the co-evolution/change-coupling of software artifacts, especially in the case of database-related changes.
Since there are hardly works or established tools considering the co-evolution of schema and the code accessing it, we are investigating this topic.

As roundcube is one major project in the open-source-community and is also supporting several databases, I have some questions: 
We found out that schema related changes were often committed together - across all databases .
So in your case, some schema-changes were done for mssql, mysql, oracle, postgres and sqlite simultaneously.
1) Could you describe the common process of introducing these schema changes or do you have a manual for that?
2) Is there any tool in use, which supports this process automatically or is it done manually?
3) How much time is consumed when introducing schema changes in your project?
4) Which problems occur when changing the schema?

Hopefully you can spend some time to answer these questions, I would be very grateful.

Best regards

Atalay Karatay