[liyanchang]

I’ll openly admit that we don’t have everything figured out. You’re absolutely right that currently, we constrain ourselves on what we migrate to admittedly simple migrations.

I think there’s a whole set of problems to be solved in this space and frankly, I’m as surprised as anyone that given how SQL is declarative, we use procedural code to do migrations so part of my post was hoping people would tell me what tool I should be using or how this approach fails over time. So your examples are really helpful for me as I think through if it’s possible to do automatically, workaround, or get by without.

It seems to me that we just lack the ability to express these transitions mathematically that can help us do them. And of those, there’s probably only a subset which are possible to do without taking downtime.

In particular, the class of migrations that you outlines are a combination of DDL and DML changes and also have quite a bit of code complexity to do without downtime. It’s definitely a current weakness.