Ruby: Rails Active Record

Defines the schema with Active Record migrations DSL and uses a model. In a Rails application the same change is DATABASE_URL (or host: in config/database.yml). The code is the same against the original database and against MachSQL; only the address changes.

The only change

DATABASE_URL=postgres://app:${DB_PASSWORD}@old-postgres:5432/app
DATABASE_URL=postgres://app:${DB_PASSWORD}@machsql-host:5432/app

Nothing else changes: not the code, not the driver, not its version, not the SQL.

Versions

• Ruby 4.0
• activerecord 8.1.4 (Rails 8.1)
• pg 1.7.0

Run

bundle install
export DATABASE_URL=postgres://app:${DB_PASSWORD}@machsql-host:5432/app
bundle exec ruby main.rb

Expected output: inserted todo <id>, <n> open.

Source

The program as it is kept and tested in the Mach Database for PostgreSQL repository; highlighted lines read the connection setting.

main.rb

# Active Record (Rails 8.1) outside a Rails application.
require "active_record"

ActiveRecord::Base.establish_connection(ENV.fetch("DATABASE_URL"))

unless ActiveRecord::Base.connection.table_exists?(:ar_todos)
  ActiveRecord::Schema.define do
    create_table :ar_todos do |t|
      t.string :title, null: false
      t.boolean :done, null: false, default: false
    end
  end
end

class Todo < ActiveRecord::Base
  self.table_name = "ar_todos"
end

todo = Todo.create!(title: "write the examples")
puts "inserted todo #{todo.id}, #{Todo.where(done: false).count} open"

Gemfile

source "https://rubygems.org"

gem "activerecord", "8.1.4"
gem "pg", "1.7.0"