I'm not sure why you're getting downvoted, this is a fine question. One approach is to use Point In Time Recovery. When you run your migration, you take note

I'm not sure why you're getting downvoted, this is a fine question. One approach is to use Point In Time Recovery. When you run your migration, you take note of the LSN (the point in the WAL stream) just before you make your changes. Then you can roll back to the point in time right before you applied the migration. Note that you will need some other mechanism for restoring any data you added after the migration point.