Cached lookup

cached.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "activerecord", "~> 7.0.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)
ActiveRecord::Schema.define do
  create_table :organizations, force: true do |t|
  end

  create_table :users, force: true do |t|
    t.string :name
  end

  create_table :memberships, force: true do |t|
    t.references :organization
    t.references :user
  end
end

class Organization < ActiveRecord::Base
  has_many :memberships
  has_many :users, through: :memberships

  def member?(user)
    user.has_attribute?(:cached_member) && user.cached_member
  end
end

class User < ActiveRecord::Base
  has_many :memberships
end

class Membership < ActiveRecord::Base
  belongs_to :organization
  belongs_to :user
end

org1, org2 = *2.times.map { Organization.create! }
org1.users.create!([{ name: "Org1Foo" }, { name: "Org2Bar" }])
org2.users.create!([{ name: "Org1Foo" }, { name: "Org2Bar" }, { name: "Org2Baz"}])

# Reload to ensure nothing is cached.
org1.reload
org2.reload

# Get a list of the queries that are executed to ensure we're not hitting the
# database more than we need to.
queries = []
ActiveSupport::Notifications.subscribe("sql.active_record") do |*, payload|
  queries << payload[:sql]
end

# Iterate through and call member? for each user.
org1.users.select("users.*, TRUE as cached_member").each { |user| puts org1.member?(user) }
org2.users.each { |user| puts org1.member?(user) }

# Check that only the two user queries were executed.
p queries