Understanding Database Connections in Rails: When and Why to Use Different Approaches

• Increased Complexity: It can become challenging to maintain and test your application when database connections are scattered throughout the codebase.
• Security Concerns: Dynamically switching databases can introduce security risks if not implemented carefully, as it could potentially expose sensitive data unintentionally.
• Limited Flexibility: In real-world scenarios, you might often have more complex requirements, such as connecting specific models to different databases based on specific criteria, which wouldn't be easily achievable with this approach.

Therefore, it's usually better to follow established practices and design patterns for managing database connections in Rails. Here are two widely used solutions:

Multiple Databases with Sharding:

• If your application requires connecting to multiple databases, the recommended approach is to use Rails' built-in support for multiple databases with sharding. This allows you to configure different database connections for specific models or groups of models based on your application's needs.

# config/databases.yml
default: &default
  adapter: postgresql
  database: my_app_db
  username: postgres
  password: my_secret_password

sharded_db:
  <<: *default
  database: sharded_db

# In your models:
class User < ApplicationRecord
  establish_connection :default
end

class Product < ApplicationRecord
  establish_connection :sharded_db
end

Database Environments:

• If you need to switch the database based on your environment (e.g., development, test, production), you can leverage Rails' environment variables to configure the database connection dynamically.

# config/environments/development.rb
config.database = {
  adapter: 'postgresql',
  database: 'my_app_db_dev',
  username: 'postgres',
  password: 'my_dev_password'
}

# config/environments/test.rb
config.database = {
  # ... test database configuration
}

# config/environments/production.rb
config.database = {
  # ... production database configuration
}

In these scenarios, all models connect to the configured database based on the environment, making it a more controlled and secure approach.