Just recently, a client of ours requested a software update to address a certain issue. The update went smoothly enough, with the biggest step being the update to their database. We have a utility that automates a Red Gate compare and updates based on differences. Usually this works smoothly and requires only a bit of coaxing once in a while. The only problem is that while the update seemed normal, it isn't smart enough to notice changes in the old version so it overwrites any existing database object with the new version.
Soon, the "bug reports" started rolling in...
To make a long story short, I can't help but wonder if there is a better way to extend a data layer with customer-specific changes. We already have a mechanism which which we extend a few key stored procedures, but it's only a 'if exists run XYZ' call to an extender proc. These extender procedures are ignored during an update and are thus safe from overwriting, but they are of somewhat limited value for coupling in additional functionality. I have begun looking at borrowing a few pages from the OO playbook for this problem. Specifically, I think some good'ole polymorphism would allow customers to extend our product in a safe way.