[tomhoule]

No question that there are cases where down migrations are a solution that works. In my experience though, these cases are more limited than you might think. There are a lot of presuppositions that need to hold for a down migration to "just work":

- The migration is reversible in the first place. It did not drop or irreversibly alter anything (table/column) the previous version of the application code was using.

- The up migration ran to the end, it did not fail at some step in the middle.

- The down migration actually works. Are your down migrations tested?

- You have a small enough data set that the rollback will not take hours/bring down your application by locking tables.

There are two major avenues for migration tools to be more helpful when a deployment fails:

- Give a short path to recovery that you can take without messing things up even more in a panic scenario

- Guide you towards patterns that can make deploying and recovering from bad deployment painless, i.e. forward-only thinking, expand-and-contract pattern, etc.

We're looking into how we can best help in these areas. It could very well mean we'll have down migrations (we're hearing users who want them, and we definitely want these concerns addressed).