Check db/migrate/ instead of schema.rb

[chuckd]

This seems to me the correct way to check for migrations: diff the db/migrate/ folders.

It avoids the problems with schema_format :sql entirely. No need to try and read the schema_format setting or check either/or schema.rb/structure.sql. Fixes #57, #59 and #74.

[nathanvda]

On a side-note: rake db:migrate knows exactly how to check if a migration needs to be executed or not. Sooooooo I am not sure, but it seems a bit silly to be checking a complete folder for changes, if rails has already solved this.

If we check only a single file, I can get there is a possible performance enhancement (just skip if you know nothing has changed). But this is what caused all the problems in the first place :)

I am also using schema_format :sql so I am definitely interested in a fix. Just thinking out loud.

[chuckd]

@nathanvda the main gain is not having to boot rails, against which a recursive diff is nothing: for what it's worth, a folder diff here (with 94 migrations) takes 17 milliseconds, vs 3.7 seconds for the no-op migrate.

[chuckd]

@rstacruz any chance of a decision on this one? I just realised I've been running this accidentally for the past month through bodgy direct edit of the gem. It's been working fine for me...

[Kriechi]

I think this is better then the current solution. 👍 for merging this!

Although, as mentioned, I'd probably spend 4 seconds doing it the correct way - spinning up Rails and let the Rails people decide if we should migrate something.

[Kriechi]

Additional note:
capistrano-rails now also uses a db/migrate/ folder diff to migrate on demand.
https://github.com/capistrano/rails/blob/master/lib/capistrano/tasks/migrations.rake#L10

[gabskoro]

I agree, it's better to check the migrate folder :)