Rails migration management - best practices ?

Question

What are best practices for migration management?

For instance, when debugging a migration, do you edit the original migration or add an edit migration before committing to the repository? Thanks!

Answer 1

I tend to edit the original migration as long as it is a) the last migration and b) not in source control. This presents a clean migration path for all other consumers of the code. The important thing is that your migrations should be able to run without error from whatever database state is the earliest that you can expect to encounter.

Answer 2

If you are working with multiple developers, editing an existing migration can be dangerous.

If your coworker has already migrated the original migration, then when he updates he will not pick up the new code and hilarity will ensue. This is a very difficult issue to track down. Error on the side of being a good denizen and just create an updated migration.

Answer 3

Only ever edit an existing migration if you can verify that it has not yet been run by other developers or some automated build setup. To be on the safe side, you shouldn't edit a commited migration file unless the bug was so severe that the migration wouldn't run in the first place (in which case why did you commit it?)

Also, special care has to be taken with migrations calling code from elsewhere in your application so that when they are run, they are run using the correct version of the code. Otherwise subtle changes in your models can really screw up your earlier migrations.

Answer 4

Even after reading this and the answers below, I just learned the hard way. Not to edit the original. You end up losing track your development process and it's hard to get back under control.