DZone Snippets is a public source code repository. Easily build up your personal collection of code snippets, categorize them with tags / keywords, and share them with the world

Snippets has posted 5883 posts at DZone. View Full User Profile

Tip: Recover From Failed Rails 'down' Migration

  • submit to reddit

The second tip is handy when you’re working on a migration. I find that the process (for me) works like this:

    * Create the migration and run it.
    * Discover I forgot something.
    * Migrate down to the previous schema version.
    * Change the migration and run it again.

(Repeat as necessary.) However, being the imperfect programmer that I am, I find that I often implement the #down method incorrectly, forgetting to drop a table or remove a column. Thus, when I try to run the migration again, it fails saying that the table/column already exists.

Using script/console and ActiveRecord::Schema, it becomes a cinch to clean up the artifacts:
ActiveRecord::Schema.define do
    drop_table :foos
    remove_column :bars, :blitz
    remove_column :bars, :things