The objective of this project is to provide a boilerplate to help us practice some queries and concepts using ActiveRecord and pure SQL using PostgreSQL as our base.
- Ruby 3.3.0
- PostgreSQL (recommended >=16)
- Docker and
docker-compose(optional)
- Running both App and Postgres in Docker
docker-compose up [-d]
# And to open the Rails Console
docker-compose run --rm app rails c- Running only Postgres in Docker
docker-compose up db [-d]
# The database credentials are needed to connect to the postgres container
# The easiest way is to define the DATABASE_URL environment variable
export DATABASE_URL=postgres://postgres:secret_password@localhost
bundle install
bundle exec rails db:create db:setup
bundle exec rails cThe project db/seeds.rb file contains a script to populate with a randomized number of records in order to test the queries.
There is a list of commented model classes we will use during the exercises. Uncomment them as we go and rerun the bundle exec rails db:seed to populate your database.
The project also uses the faker and factory_bot_rails gems to generate the dummy data.
During the workshop, we'll create a few queries and we should add them under the app/queries/ directory. There we have the application_query.rb class, which has a few helper methods, we must implement the #call method that executes the query and returns the expected response.
We can write the implementation using the model methods, but it is preferred raw SQL for a better understanding of the concepts (we can convert back and forth later on using the ApplicationRecord#to_sql method to see the generated query too)
You shouldn't limit yourself to one way or another, if you have time and are willing, you can implement both and just swap between the implementations in the #call method and compare the outputs.
class ExampleQuery < ::ApplicationQuery
def call
execute_query load_query('day_one/complex_query.sql')
end
end
class OtherExampleQuery < ::ApplicationQuery
def call
execute_query 'SELECT id, name FROM people;'
end
end
class AndYetAnotherQuery < ::ApplicationQuery
def call
Person.select(:id, :name).map(&:attributes).to_a
end
end
class MultipleImplementationsQuery < ::ApplicationQuery
def call
return active_record_implementation if options[:ar_implementation]
raw_sql_implementation
end
private
def active_record_implementation
# cool implementation
end
def raw_sql_implementation
# even cooler implementation
end
end