makimodoshi

makimodoshi is a Rails gem that automatically rolls back excess database migrations when starting rails s. It solves the common pain point of branch switching leaving behind applied migrations that no longer exist in the current branch.

The Problem

When working on a Rails app with multiple branches:

1. You run db:migrate on feature-A, applying new migrations
2. You switch to main — the migration files disappear, but the DB changes remain
3. rails s starts with an inconsistent state: schema.rb says one thing, the DB says another
4. You get mysterious errors, or worse, you don't notice and keep developing on a broken foundation

The usual fix is db:rollback (hoping the files still exist) or db:reset (losing all seed data). Both are tedious, error-prone, and easy to forget.

The Solution

makimodoshi hooks into rails s startup and automatically detects when the database is ahead of schema.rb. When it finds excess migrations, it rolls them back using stored migration source code — even if the original migration files have been deleted by a branch switch.

Installation

Add to your Gemfile in the development group:

group :development do
  gem "makimodoshi", git: "https://github.com/s4na/makimodoshi.git"
end

Then run:

$ bundle install

That's it. No generators, no initializers, no configuration needed.

Note: This gem is not published on RubyGems. GitHub リポジトリから直接インストールしてください。

How It Works

1. Automatic Storage (db:migrate)

Every time you run db:migrate, makimodoshi saves a copy of each migration's source code to a hidden database table (_makimodoshi_migrations). This table is:

• Automatically excluded from schema.rb dumps (won't pollute your schema)
• Created on first use (no setup migration required)

2. Automatic Rollback (rails s)

When rails s starts, makimodoshi compares the schema.rb version with the database's schema_migrations table. If the DB is ahead, it automatically rolls back the excess migrations using the stored source code.

$ rails s
[makimodoshi] DB is ahead of schema.rb by 2 migration(s): 20240301000000, 20240201000000
[makimodoshi] Auto-rolling back...
[makimodoshi] Rolling back 20240301000000 (20240301000000_add_tags_to_posts.rb)...
[makimodoshi] Rolled back 20240301000000.
[makimodoshi] Rolling back 20240201000000 (20240201000000_create_comments.rb)...
[makimodoshi] Rolled back 20240201000000.
[makimodoshi] Auto-rollback complete.
=> Booting Puma
...

3. Safety

• Development only: All DB operations are restricted to Rails.env.development?. In any other environment, the gem does nothing and prints a warning.
• No schema pollution: The hidden table is excluded from schema.rb via SchemaDumper.ignore_tables.
• No-op when in sync: If the DB matches schema.rb, startup cost is minimal (one file read + one DB query).

Rake Tasks

Check stored migrations

$ rails makimodoshi:status
[makimodoshi] Stored migrations:
  Version          Filename                                           Migrated At
  ---------------- -------------------------------------------------- --------------------
  20240301000000   20240301000000_add_tags_to_posts.rb                2024-03-01 12:00:00
  20240201000000   20240201000000_create_comments.rb                  2024-02-01 12:00:00

Rollback one migration

$ rails makimodoshi:rollback

Roll back a specific version:

$ rails makimodoshi:rollback VERSION=20240201000000

Rollback all excess migrations

$ rails makimodoshi:rollback_all

Typical Workflow

# On feature-A branch
$ rails db:migrate        # Migrations are applied and stored by makimodoshi

$ git checkout main       # Migration files disappear, DB still has the changes

$ rails s                 # makimodoshi detects the mismatch and auto-rolls back

Requirements

• Ruby >= 2.7
• Rails >= 6.1
• schema.rb based projects (structure.sql is not supported)

Limitations

• structure.sql is not supported. Only projects using schema.rb are supported.
• Pre-installation migrations are not covered. Migrations applied before installing makimodoshi have no stored source code. If rollback is attempted, it will be skipped with a warning.
• Development only. This gem is intentionally restricted to the development environment. It will never modify your production database.

Development

$ git clone https://github.com/s4na/makimodoshi.git
$ cd makimodoshi
$ bundle install
$ bundle exec rspec

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/s4na/makimodoshi.

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

License

The gem is available as open source under the terms of the MIT License.