additional_databases_rails.md

Commands examples

If the namespace is not used then the commands will perform on top of the default database. bundle exec rake db:create bundle exec rake db:migrate

By using the namespace we are going to use all the configuration for our alternate DB. bundle exec rake store:db:create bundle exec rake store:db:migrate

Notes

• From here having a more complex structure with more than one alternative database should be easy.

TODO

• hey for Rails 4 change Rails.application.config.paths['db/seeds'] for Rails.application.config.paths['db/seeds.rb'] and add ActiveRecord::Migrator.migrations_paths = 'db_store/migrate' for work store:db:seed

• add desc '' for actual tasks, so autocomplete finds them

data_store_base.rb

# models/data_store_base.rb

# Public: Provide a base class for accessing the store database.
# All models inheriting from this class will use by default the data store DB.
class DataStoreBase < ActiveRecord::Base

  # Tell Active Record (AR) to not look up for a table called like this class,
  # since this class is only used to add custom config for AR
  self.abstract_class = true

  databases = YAML::load(IO.read('config/database_store.yml'))
  establish_connection(databases[Rails.env])

end

database.yml

# config/database.yml

development: &development
  adapter: sqlite3
  database: db/administrator_development.sqlite3
  pool: 5
  timeout: 5000

test:
  adapter: sqlite3
  database: db/administrator_test.sqlite3
  pool: 5
  timeout: 5000

database_store.yml

# config/database_store.yml

development: &development
  adapter: sqlite3
  database: db_store/data_store_development.sqlite3
  pool: 5
  timeout: 5000

test:
  adapter: sqlite3
  database: db_store/data_store_test.sqlite3
  pool: 5
  timeout: 5000

databases.rake

# lib/tasks/databases.rake

# Public: This Rake file tries to add what rails provides on the
# databases.rake but for building on top of custom databases.
# Basically we get the nice db:migrate but for using it on a different DB than
# the default, by calling it with the namespace defined here.
#
# In order to be able to use the default rails rake commands but on a different
# DB, we are first updating the Rails.application.config.paths and then
# calling the original rake task. Rails.application.config.paths is getting
# loaded and available as soon as we call rake since the rakefile in a rails
# project declares that. Look at Rakefile in the project root for more details.


# Public: Access to the same commands you do for DB operations,
# like db:drop, db:migrate but using the store namespace, this will
# execute on top of the store DB.
namespace :store do

  desc "Configure the variables that rails need in order to look up for the db
    configuration in a different folder"
  task :set_custom_db_config_paths do
    # This is the minimum required to tell rails to use a different location
    # for all the files related to the database.
    ENV['SCHEMA'] = 'db_store/schema.rb'
    Rails.application.config.paths['db'] = ['db_store']
    Rails.application.config.paths['db/migrate'] = ['db_store/migrate']
    Rails.application.config.paths['db/seeds'] = ['db_store/seeds.rb']
    Rails.application.config.paths['config/database'] = ['config/database_store.yml']
  end

  namespace :db do
    task :drop => :set_custom_db_config_paths do
      Rake::Task["db:drop"].invoke
    end

    task :create => :set_custom_db_config_paths do
      Rake::Task["db:create"].invoke
    end

    task :migrate => :set_custom_db_config_paths do
      Rake::Task["db:migrate"].invoke
    end

    task :rollback => :set_custom_db_config_paths do
      Rake::Task["db:rollback"].invoke
    end

    task :seed => :set_custom_db_config_paths do
      Rake::Task["db:seed"].invoke
    end

    task :version => :set_custom_db_config_paths do
      Rake::Task["db:version"].invoke
    end

    namespace :schema do
      task :load => :set_custom_db_config_paths do
        Rake::Task['db:schema:load'].invoke
      end
    end
  end
  
  namespace :test do
    task :prepare => :set_custom_db_config_paths do
      Rake::Task["db:test:prepare"].invoke
    end
  end

end