SeedMigration

Harry's Data Migrations are a way to manage changes to seed data in a rails app in a similar way to how schema migrations are handled.

Intro

A data migration library, similar to rails built-in schema migration. It also auto generates a db/seeds.rb file, similar to how schema migrations generate the db/schema.rb file. Using this auto generated seed file makes it quick and easy to setup new environments, usually development or test.

Installation

Add gem 'seed_migration' to your Gemfile:

gem 'seed_migration'

Usage

Install and run the internal migrations

rake seed_migration:install:migrations
rake db:migrate

That will create the table to keep track of data migrations.

Generate a new migration

You can use the generator :

rails g seed_migration AddFoo

A new file will be created under db/data/ using rails migration convention:

db/data/20140407162007_add_foo.rb

You'll need to implement the #up method and if you need to be able to rollback, the #down method.

Running the migrations

To run all pending migrations, simply use

rake seed:migrate

If needed, you can run a specific migration:

rake seed:migrate MIGRATION=20140407162007_add_foo.rb

Rollback

Rolling back the last migration is as simple as:

rake seed:rollback

You can rollback more than one migration at the same time:

rake seed:rollback STEP=3 # rollback last 3 migrations

Or rollback a specific migration:

rake seed:rollback MIGRATION=20140407162007_add_foo.rb

Registering models

By default no models are registered, so running seed migrations won't update the seeds file. You have to manually register the models in the configuration file.

Simply register a model:

SeedMigration.register Product

You can customize the 'seeded' attribute list:

SeedMigration.register User do
  exclude :id, :password
end

This will create a seeds.rb containing all User and Product in the database:

# encoding: UTF-8
# This file is auto-generated from the current content of the database. Instead
# of editing this file, please use the migrations feature of Seed Migration to
# incrementally modify your database, and then regenerate this seed file.
#
# If you need to create the database on another system, you should be using
# db:seed, not running all the migrations from scratch. The latter is a flawed
# and unsustainable approach (the more migrations you'll amass, the slower
# it'll run and the greater likelihood for issues).
#
# It's strongly recommended to check this file into your version control system.

ActiveRecord::Base.transaction do
  Product.create("created_at"=>"2014-04-04T15:42:24Z", "id"=>1, "name"=>"foo", "updated_at"=>"2014-04-04T15:42:24Z")
  Product.create("created_at"=>"2014-04-04T15:42:24Z", "id"=>2, "name"=>"bar", "updated_at"=>"2014-04-04T15:42:24Z")
  # ...
  User.create("created_at"=>"2014-04-04T15:42:24Z", "id"=>1, "name"=>"admin", "updated_at"=>"2014-04-04T15:42:24Z")
  # ...
end

SeedMigration::Migrator.bootstrap(20140404193326)

Note that seeds.rb is only generated in development mode. Production data will not be dumped in this process.

Adding seed_migrations to an existing app

If your app already contains seeds, using this gem could cause some issues. Here is the basic process to follow to ensure a smooth transition:

• Clean your local database, and seed it, that can be done with rake db:reset
• register all the models that were created in the original seeds file
• run rake seed:migrate
• At this point, your seeds file will be rewritten with all the create! statements
• Commit/Push the updated seeds file

Deployment notes

It is recommended to add the rake seed:migrate to your deploy script, so each new data migrations is ran upon new deploys. You can enable the extend_native_migration_task option to automatically run rake seed:migrate after rake db:migrate.

For Capistrano 3.x support, add this to your Capfile

require 'capistrano/seed_migration_tasks'

which provides the two cap tasks, which you can add to your deploy script or run on the command line:

cap {stage} seed:migrate
cap {stage} seed:rollback

Example

rails g seed_migration AddADummyProduct

class AddADummyProduct < SeedMigration::Migration
    def up
        Product.create!({
            :asset_path => "valentines-day.jpg",
            :title => "Valentine's Day II: the revenge!",
            :active => false,
            :default => false,
        }, :without_protection => true)
    end

    def down
        Product.destroy_all(:title => "Valentine's Day II: the revenge!")
    end
end

Configuration

Use an initializer file for configuration.

List of available configurations :

• extend_native_migration_task (default=false)
• ignore_ids (default=false)
• migration_table_name (default='seed_migration_data_migrations'): Override the table name for the internal model that holds the migrations

example:

# config/initializers/seed_migration.rb

SeedMigration.config do |c|
    c.migration_table_name = 'data_migrations'
    c.extend_native_migration_task = true
end

SeedMigration.register User do
  exclude :id, :password
end
SeedMigration.register Product

Compatibility

At the moment, we rely by default on

ActiveRecord::Base.connection.reset_pk_sequence!

which is pg only.

If you need to use this gem with another database, use the ignore_ids configuration.

Runnings tests

RAILS_ENV=test bundle exec rake app:db:reset
bundle exec rspec spec

Contributing

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 new Pull Request