数据库模式不同步 - 需要在不丢失数据的情况下获取最新信息

The problem: we have one application that has a portion which is used by a very small subset of the total users, and that part of the application is running off of a separate database as well. In a perfect world, the schemas of the two databases would be synced up, but such is not the case. Some migrations have been run on the smaller database, most haven't; and furthermore, there is nothing such as revision number to be able to easily identify which have and which haven't. We would like to solve this quandary for future projects. During a discussion we've come up with the following possible plan of action, and I am wondering if anyone knows of any project which has already solved this problem:The problem: we have one application that has a