Run data migrations alongside schema migrations.

Data migrations are stored in db/data. They act like schema migrations, except they should be reserved for data migrations. For instance, if you realize you need to titleize all your titles, this is the place to do it.

With data-migrate you can generate your migrations for data as you would schema in your regular work flow.

For setting tasks that don't require any intermediate AR activity, like dev and test, you stick with db:migrate. For production and QA, you change their scripts to db:migrate:with_data. Of course you want to test your migration, so you have the choice of db:migrate:with_data or data:migrate to just capture that data change.

Data migrations are stored in db/data. They act like schema migrations, except they should be reserved for data migrations. For instance, if you realize you need to titleize all yours titles, this is the place to do it. Running any of the provided rake tasks also creates a data schema table to mirror the usual schema migrations table to track all migrations.

Support Rails 6.1 through 7.1

If you've installed previous to v1.1.0, you'll want to delete the create_data_migrations_table migration.

Add the gem to your project

# Gemfile
gem 'data_migrate'

Then bundle install and you are ready to go.

So you know, when you use one of the provide rake tasks, a table called data_migrations will be created in your database. This is to mirror the way the standard db rake tasks work.

You can generate a data migration as you would a schema migration:

rails g data_migration add_this_to_that

$> rake -T data
rake data:abort_if_pending_migrations          # Raises an error if there are pending data migrations
rake data:dump                                 # Create a db/data_schema.rb file that stores the current data version
rake data:forward                              # Pushes the schema to the next version (specify steps w/ STEP=n)
rake data:migrate                              # Migrate data migrations (options: VERSION=x, VERBOSE=false)
rake data:migrate:down                         # Runs the "down" for a given migration VERSION
rake data:migrate:redo                         # Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x)
rake data:migrate:status                       # Display status of data migrations
rake data:migrate:up                           # Runs the "up" for a given migration VERSION
rake data:rollback                             # Rolls the schema back to the previous version (specify steps w/ STEP=n)
rake data:schema:load                          # Load data_schema.rb file into the database without running the data migrations
rake data:version                              # Retrieves the current schema version number for data migrations
rake db:abort_if_pending_migrations:with_data  # Raises an error if there are pending migrations or data migrations
rake db:forward:with_data                      # Pushes the schema to the next version (specify steps w/ STEP=n)
rake db:migrate:down:with_data                 # Runs the "down" for a given migration VERSION
rake db:migrate:redo:with_data                 # Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x)
rake db:migrate:status:with_data               # Display status of data and schema migrations
rake db:migrate:up:with_data                   # Runs the "up" for a given migration VERSION
rake db:migrate:with_data                      # Migrate the database data and schema (options: VERSION=x, VERBOSE=false)
rake db:rollback:with_data                     # Rolls the schema back to the previous version (specify steps w/ STEP=n)
rake db:schema:load:with_data                  # Load both schema.rb and data_schema.rb file into the database
rake db:structure:load:with_data               # Load both structure.sql and data_schema.rb file into the database
rake db:version:with_data                      # Retrieves the current schema version numbers for data and schema migrations

Tasks work as they would with the 'vanilla' db version. The 'with_data' addition to the 'db' tasks will run the task in the context of both the data and schema migrations. That is, rake db:rollback:with_data will check to see if it was a schema or data migration invoked last, and do that. Tasks invoked in that space also have an additional line of output, indicating if the action is performed on data or schema.

With 'up' and 'down', you can specify the option 'BOTH', which defaults to false. Using true, will migrate both the data and schema (in the desired direction) if they both match the version provided. Again, going up, schema is given precedence. Down its data.

When using rake db:migrate:with_data migrations will be run in ascending order by their version. For example, if you have a data migration with version 20230410000000 and a schema migration with version 20230415000000, expect the data migration to run first.

rake db:migrate:status:with_data provides an additional column to indicate which type of migration.

data_migrate respects ActiveRecord::Base.dump_schema_after_migration. If it is set to false, data schema file will not be generated

By default, data migrations are added to the db/data/ path. You can override this setting in config/initializers/data_migrate.rb

DataMigrate.configure do |config|
  config.data_migrations_path = 'db/awesomepath/'
  config.data_template_path = Rails.root.join("lib", "awesomepath", "custom_data_migration.rb")
  config.db_configuration = {
    'host' => '127.0.0.1',
    'database' => 'awesome_database',
    'adapter' => 'mysql2',
    'username' => 'root',
    'password' => nil,
  }
  config.spec_name = 'primary'
end

The gem comes with a capistrano task that can be used instead of capistrano/rails/migrations.

Just add this line to your Capfile:

require 'capistrano/data_migrate'

From now on capistrano will run rake db:migrate:with_data in every deploy.

This gem also has a initial support for adding data migrations inside Rails engines. Inside the Engine's class initializer (the one that inherits from Rails::Engine, usually inside engines/ENGINE_NAME/lib/engine.rb) you need to add something like this:

module EngineName
  class Engine < ::Rails::Engine
    initializer :engine_name do |app|
      ::DataMigrate.configure do |data_migrate|
        default_path = ::DataMigrate::Config.new.data_migrations_path
        data_migrate.data_migrations_path = [default_path, root.join('db', 'data')]
      end
    end
  end
end

Then, in the Engine's db/data folder, you can add data migrations and run them as usual.

Run tests for a specific version of Rails

bundle exec appraisal install
bundle exec appraisal rails-6.1 rspec
bundle exec appraisal rails-7.0 rspec
bundle exec appraisal rails-7.1 rspec

Andrew J Vargo Andrew was the original creator and maintainer of this project!

Jeremy Durham for fleshing out the idea and providing guidance.

You! Yes, you. Thanks for checking it out.