How can I rollback a specific migration?

I have the migration file db\migrate\20100905201547_create_blocks.rb.

How can I spec开发者_StackOverflow中文版ifically rollback that migration file?

rake db:rollback STEP=1

Is a way to do this, if the migration you want to rollback is the last one applied. You can substitute 1 for however many migrations you want to go back.

For example:

rake db:rollback STEP=5

Will also rollback all the migration that happened later (4, 3, 2 and also 1).

To roll back all migrations back to (and including) a target migration, use: (This corrected command was added after all the comments pointing out the error in the original post)

rake db:migrate VERSION=20100905201547

In order to rollback only one specific migration (out of order) use:

rake db:migrate:down VERSION=20100905201547

Note that this will NOT rollback any interceding migrations -- only the one listed. If that is not what you intended, you can safely run rake db:migrate and it will re-run only that one, skipping any others that were not previously rolled back.

And if you ever want to migrate a single migration out of order, there is also its inverse db:migrate:up:

rake db:migrate:up VERSION=20100905201547

rake db:migrate:down VERSION=20100905201547

will roll back the specific file.

To find the version of all migrations, you can use this command:

rake db:migrate:status

Or, simply the prefix of the migration's file name is the version you need to rollback.

See the Ruby on Rails guide entry on migrations.

To rollback the last migration you can do:

rake db:rollback

If you want to rollback a specific migration with a version, you should do:

rake db:migrate:down VERSION=YOUR_MIGRATION_VERSION

For example, if the version is 20141201122027, you will do

rake db:migrate:down VERSION=20141201122027

to rollback that specific migration.

You can rollback your migration by using rake db:rollback with different options. The syntax will be different according to your requirements.

If you want to rollback just the last migration, then you can use either

rake db:rollback

or

rake db:rollback STEP=1

If you want rollback number of migrations at once, then you simply pass an argument:

rake db:rollback STEP=n

where n is number of migrations to rollback, counting from latest migration.

If you want to rollback to a specific migration, then you should pass the version of the migration in the following:

rake db:migrate:down VERSION=xxxxx

where xxxxx is the version number of the migration.

Use:

rake db:migrate:down VERSION=your_migrations's_version_number_here

The version is the numerical prefix on the migration's file name.

How to find the version:

Your migration files are stored in your rails_root/db/migrate directory. Find the appropriate file up to which you want to rollback and copy the prefix number.

For example:

File name: 20140208031131_create_roles.rb

Then the version is 20140208031131.

Rolling back the last migration:

# rails < 5.0
rake db:rollback

# rails >= 5.0
rake db:rollback
# or
rails db:rollback

Rolling back the last n number of migrations

# rails < 5.0
rake db:rollback STEP=2

# rails >= 5.0
rake db:rollback STEP=2
# or
rails db:rollback STEP=2

Rolling back a specific migration

# rails < 5.0
rake db:migrate:down VERSION=20100905201547

# rails >= 5.0
rake db:migrate:down VERSION=20100905201547
# or
rails db:migrate:down VERSION=20100905201547

To rollback the last migration you can do:

rake db:rollback

If you want to rollback a specific migration with a version you should do:

rake db:migrate:down VERSION=YOUR_MIGRATION_VERSION

If the migration file you want to rollback was called db/migrate/20141201122027_create_some_table.rb, then the VERSION for that migration is 20141201122027, which is the timestamp of when that migration was created, and the command to roll back that migration would be:

rake db:migrate:down VERSION=20141201122027

To roll back all migrations up to a particular version (e.g. 20181002222222), use:

rake db:migrate VERSION=20181002222222

(Note that this uses db:migrate -- not db:migrate:down as in other answers to this question.)

Assuming the specified migration version is older than the current version, this will roll back all migrations up to, but not including, the specified version.

For example, if rake db:migrate:status initially displays:

  (... some older migrations ...)
  up      20181001002039  Some migration description
  up      20181002222222  Some migration description
  up      20181003171932  Some migration description
  up      20181004211151  Some migration description
  up      20181005151403  Some migration description

Running:

rake db:migrate VERSION=20181002222222

Will result in:

  (... some older migrations ...)
  up      20181001002039  Some migration description
  up      20181002222222  Some migration description
  down    20181003171932  Some migration description
  down    20181004211151  Some migration description
  down    20181005151403  Some migration description

Reference: Migrate or revert only some migrations

If it is a reversible migration and the last one which has been executed, then run rake db:rollback. And you can always use the version.

For example, if the migration file is 20140716084539_create_customer_stats.rb, the rollback command will be:

rake db:migrate:down VERSION=20140716084539

If you are using Ruby on Rails 3

Step: 1 (check the last migration)

bundle exec rake db:migrate:status

Step: 2 (roll back the last migration)

bundle exec rake db:rollback

Now, you can revert the migration with safety one by one.

For a specific migration

rails d migration <migration_name>

For reverting multiple migrations

bundle exec rake db:rollback STEP=n

where n is how many migrations you want to rollback.

Example: bundle exec rake db:rollback STEP=5

Migrations change the state of the database using the command

bundle exec rake db:migrate

We can undo a single migration step using

bundle exec rake db:rollback

To go all the way back to the beginning, we can use

bundle exec rake db:migrate VERSION=0

As you might guess, substituting any other number for 0 migrates to that version number, where the version numbers come from listing the migrations sequentially.

A migration file looks like this,

 20221213051020_my_migrations

In this case, the model name should be MyMigration. The migration ends with a plural word, so it ends with migrations.

To roll back this particular migration, you have to understand that the first part of the migration name (number in front of the migration name) is the migration number.

To roll back this migration, just open the terminal and write,

rake db:migrate:down VERSION=migration_number

So finally, you have to actually type in the terminal to roll back this particular migration,

Write the below command on terminal to rollback a particular migration, upper command is just to explain you

rake db:migrate:down VERSION=20221213051020

Just remember that each migration has a different migration number, so watch carefully and copy paste or type manually.

If you want to rollback and migrate you can run:

rake db:migrate:redo

That's the same as:

rake db:rollback
rake db:migrate

Well, in rails 5 it's quite easy

rake db:migrate:status

or

rails db:migrate:status

It was modified to handle both the same way. Then just pick which version you want to roll back and then run

rake db:migrate VERSION=2013424230423

Make sure VERSION is all capital letters.

If you have a problem with any step of the migration or stuck in the middle simply, go to the migration file and comment out the lines that were already migrated.

I found these steps most useful.

To check for status, run rails db:migrate:status. Then you'll have a good view of the migrations you want to remove.

Then, run rails db:rollback to revert the changes one by one. After doing so, you can check the status again to be fully confident.

Next, if you want to remove or delete. Run rails d migration <migration_name>. This would clean up the versions you created.

After that's done, you can proceed to making new changes.

For a multiple databases configurations (RoR >= v6), you must append the database name in the command, like:

• rails db:rollback:primary, where primary is the name of the database in your config/databases.yml file, to roll back the last migration. You can make usage of the STEPS attribute here, as usual.
• rails db:migrate:down:primary VERSION=your_migration_timestamp, to revert only the provided migration version. Here primary is the name of the database too.

In addition:

When a migration you deployed long ago does not let you migrate a new one.

I work in a larger Ruby on Rails application with more than a thousand of migration files. And, it takes a month for us to ship a medium-sized feature. I was working on a feature and I had deployed a migration a month ago, and then in the review process the structure of migration and filename changed, now I try to deploy my new code, the build failed saying:

ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "my_new_field" of relation "accounts" already exists

None of the above-mentioned solutions worked for me, because the old migration file was missing and the field I intended to create in my new migration file already existed in the database. The only solution that worked for me is:

1. I scped the file to the server
2. I opened the rails console
3. I required the file in the IRB session
4. then AddNewMyNewFieldToAccounts.new.down

And then I could run the deploy build again.

If you want to revert from the last migration, use the rake db:rollback command. It's working fine for me!