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Bold of you to flat out drop down migrations.

I guess having a new up migration to cover the case is better, but its nice to have a documented way of rolling back (which would be the down migration) - without applying it programmatically. But it helps if other team members can see how a change should be rolled back ideally.

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Glenjamin gave a great answer. I’ll just add that in my experience (being responsible for the team’s database, at a few companies over the years), down migrations are NEVER helpful when a migration goes wrong. Roll-forward is the only correct model. Besides, there are plenty of migrations that cant be safely rolled back, so most “down migrations” either destroy data or don’t work (or both.)

The key here is that in production it's almost always not safe to actually apply a down migration - so it's better to make that clear than to pretend there's some way to reverse an irreversible operation.

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