Multi-Database Application

Sample Rails application for demonstrating Rails 7 - Associations across databases with disable_joins

• Ruby version: 2.7.1

• Rails version: 7.0.0

Installation/Setup

1. Clone the application on your local

git clone https://github.com/sampatbadhe/multi-db-app.git

2. cd to the passwordless-authentication-api application directory

  cd multi-db-app

3. Run bundle command to install all gems

  bundle install

4. Configure your database.yml file.

5. Run bundle exec rails db:create

6. Run bundle exec rails db:migrate

7. Run bundle exec rails db:seed. The sample data would be then loaded into application database.

8. Run the rails console using bundle exec rails console or bundle exec rails c

9. Run following operations and observe the queries.

   • Without disable_joins option

     We would have to add custom methods, as has_many :through/has_one :through associations won't work across databases.

     # Set the user
     > user = User.find_by(email: 'luke@example.com')
     # Fetch the messages of all the events of a user
     > user.event_messages
     # Fetch the latest message on the latest event of a user
     > user.latest_event_message

   • With disable_joins option

     # Set the user
     > user = User.find_by(email: 'luke@example.com')
     # We can use `has_many :through` association to fetch the messages of all the events of a user
     > user.messages
     # We can use `has_one :through` association to fetch the latest message on the latest event of a user
     > user.latest_message