Ruby on Rails: How can I revert a migration with rake db:migrate?

Question

After installing devise MODEL User i got this.

class DeviseCreateUsers < ActiveRecord::Migration
  def self.up
    create_table(:users) do |t|
      t.database_authenticatable :null => false
      t.recoverable
      t.rememberable
      t.trackable

      # t.encryptable
      # t.confirmable
      # t.lockable :lock_strategy => :failed_attempts, :unlock_strategy => :both
      # t.token_authenticatable


      t.timestamps
    end

    add_index :users, :email,                :unique => true
    add_index :users, :reset_password_token, :unique => true
    # add_index :users, :confirmation_token,   :unique => true
    # add_index :users, :unlock_token,         :unique => true
    # add_index :users, :authentication_token, :unique => true
  end

  def self.down
    drop_table :users
  end
end

Now if i do rake db:migrate the users table will be created.

How can i revert this migration, i.e. how can I delete the users table using rake again ?

Solution 1

Run the following command

rake db:migrate:down VERSION=<version>

where <version> is the version number of your migration file you want to revert.

eg. if you want to revert a migration with file name 3846656238_create_users.rb

rake db:migrate:down VERSION=3846656238

Solution 2

Just run this command:

rake db:rollback

Solution 3

I believe there are three options available for reverting migrations (they also overlap):

1. Roll down the most recent migration:

   rake db:migrate:down # Rails 2 only.

2. Roll down a number(n) of recent migrations:

   rake db:rollback STEP=n

3. Roll down to a previous, specific version:

   $ rake db:migrate:down VERSION=nnn # Rails 3 (provide version number also).

Version Number means the SHA(Secure Hash Algorithm) for the commit which is a long hexadecimal number which looks something like 886af3194768917c78e... You can see it by doing git log

You can see these commands (and others) with their descriptions by using rake -T db: which for rails 3.2 includes:

rake db:migrate         # Migrate the database (options: VERSION=x, VERBOSE=false)
rake db:migrate:status  # Display status of migrations
rake db:rollback        # Rolls the schema back to the previous version (specify steps w/ STEP=n)

Solution 4

You can do rollback and specify how many last migrations will be rollbacked, e.g.

rake db:rollback STEP=3

for 3 last migrations.

Solution 5

As an new programmer (or to other new programmers)

rake db:rollback works about half the time. I start there.

If not, rake db:migrate:down VERSION=3846656238

plug in VERSION for the version number of your migration file you want to revert.

View more solutions

Comments

[Ajedi32]

Roll down to a specific version: rake db:migrate VERSION=<version number>

[martin]

At least for rails 3.0.20, the first command is wrong. A single rake db:migrate:down aborts with the error message "VERSION is required". The recommended rake db:rollback however works.

[Michael Durrant]

As detailed in the answer, Rails 2 ONLY for the first commmand.

[Kostas Rousis]

Environment variables are case sensitive so it should be STEP and VERSION

[tf.rz]

I'm getting an UnknownMigrationVersionError but I figured out it's because my migrations are inside db/migrate/main , does anybody know a workaround for this to have db:migrate:down look inside that specific directory or the migrate subdirectories?

[johnml]

To clarify, $ rake db:migrate:down VERSION=nnn doesn't roll down to a version, it migrates down the version specified.

[Pre-alpha]

this is a more quicker and easier way, instead of looking up version numbers if you want to undo the last few migrations

[morhook]

This is just for rails 3 onwards. My life is in rails 2. So sad

[Mahesh]

@morhook This works for rails 3 also. Check the docs here guides.rubyonrails.org/v3.2/migrations.html

[morhook]

You are right! It works for both rails 2 and rails 3. Thanks @Mahesh for your input!