What is the best way to resolve Rails orphaned migrations?

Question

I have been switching between branches in a project and each of them have different migrations... This is the scenario:

$ rake db:migrate:status

 Status   Migration ID    Migration Name
--------------------------------------------------
   ...
   up     20130307154128  Change columns in traffic capture
   up     20130311155109  Remove log settings
   up     20130311160901  Remove log alarm table
   up     20130320144219  ********** NO FILE **********
   up     20130320161939  ********** NO FILE **********
   up     20130320184628  ********** NO FILE **********
   up     20130322004817  Add replicate to root settings
   up     20130403190042  ********** NO FILE **********
   up     20130403195300  ********** NO FILE **********
   up     20130403214000  ********** NO FILE **********
   up     20130405164752  Fix ap hostnames
   up     20130410194222  ********** NO FILE **********

The problem is rake db:rollback don't work at all because of the missing files...

What should I do to be able to rollback again and get rid of the NO FILE messages?

Btw, rake db:reset or rake db:drop are not an option, I cannot lose data from other tables...

Answer 1

I ended up solving the problem like this:

(1) Go to the branches that has the migration files and roll them back. This is not trivial when you have many branches which are will result in many conflicts if you try to merge them. So I use this commands to find out the branches of each orphan migration belongs to.

So, I need to find commit of the last time the migration was modified.

git log --all --reverse --stat | grep <LASTEST_ORPHAN_MIGRATION_ID> -C 10

I take the commit hash and determine which branch it belongs like this:

git branch --contains <COMMIT_HASH>

Then I can go back to that branch, do a rollback and repeat this process for all the missing files.

(2) Run migrations: checkout the branch you finally want to work on and run the migrations and you should be good to go.

Troubleshooting

I also ran in some cases where orphaned migrations where on deleted branches.

To solve this I created dummy migration files with the same migration_id of the missing files and roll them back. After that, I was able to delete they dummy migrations and have a clean migration status :)

Another alternative is deleting the missing files from the database directly:

delete from schema_migrations where version='<MIGRATION_ID>';