Example App

The example/ directory in the vdb repository is a self-contained Rails 8 blog application that ships with vdb pre-wired. It demonstrates every feature of the gem on a realistic seven-table schema.

Schema

The blog models a content platform with authors, expert reviewers, posts, threaded comments, and taxonomy tags.

Notable relationship patterns this schema exercises:

• 1:N — users → posts, posts → reviews, posts → comments
• 1:1 — users ↔ reviewers (unique index on reviewers.user_id)
• N:M via join table — posts ↔ tags through post_tags
• Self-referential — comments.parent_id for threaded replies
• Inferred FK — comments.parent_id not in add_foreign_key; vdb infers it automatically

---

vdb integration

Gemfile

group :development do
  gem 'vdb', path: '..'   # path reference to parent gem directory
end

config/routes.rb

Rails.application.routes.draw do
  mount Vdb::Engine, at: '/dev/erd'

  root 'posts#index'
  resources :posts,     only: %i[index show]
  resources :users,     only: %i[index show]
  resources :reviewers, only: %i[index show]
end

config/initializers/vdb.rb

return unless Rails.env.development?

Vdb.configure do |c|
  c.databases = { 'primary' => nil }   # auto-resolves to db/schema.rb
  c.title     = 'Blog ERD — vdb example'
end

---

Sample data

db/seeds.rb loads a realistic dataset so you can explore the app immediately after setup:

Record type	Count	Notable details
Users	4	Alice, Bob, Carol (editor), Dave — different roles
Reviewers	3	Bob (Performance), Carol (Database), Dave (Security) — verified
Posts	4	3 published, 1 draft — covering Rails, RSpec, PostgreSQL, JWT
Tags	6	Ruby, Rails, Performance, Database, Testing, Security
Post-tag joins	12	3 tags per post
Reviews	4	Ratings 4–5, mixed approved status
Comments	4	Includes one threaded reply (parent_id set)

---

ERD screenshots

Full ERD — all tables

Table search

Relationship highlighting

Application pages

---

Run the example

cd example
bundle install
bin/rails db:migrate
bin/rails db:seed
bin/rails server

Then visit:

URL	Page
http://localhost:3000	Posts index
http://localhost:3000/users	Users list
http://localhost:3000/reviewers	Reviewers list
http://localhost:3000/dev/erd	Database ERD