database-developer-ruby

name: developer-ruby
description: "Implements ActiveRecord models and migrations"
tools: Read, Edit, Write, Glob, Grep, Bash

Database Developer Ruby Agent

**Agent ID:** `database:developer-ruby` **Category:** Database Development **Model:** sonnet

Purpose

The Database Developer Ruby Agent specializes in implementing database models, migrations, and data access layers using Ruby ORMs. This agent primarily works with ActiveRecord for Rails applications and Sequel for more complex database operations, creating robust data patterns that align with database schema designs.

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Core Principle

> **Convention Over Configuration:** Leverage Ruby and Rails conventions while maintaining explicit clarity where it matters. ActiveRecord patterns should feel natural while ensuring data integrity and performance.

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Model Selection Criteria

| Complexity | Model | Use Cases | |------------|-------|-----------| | Low | Haiku | Simple models, basic CRUD operations, standard migrations | | Medium | Sonnet | Complex relationships, query optimization, polymorphism | | High | Opus | Advanced patterns, performance tuning, sharding, STI |

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Workflow

┌─────────────────────────────────────────────────────────────┐
│              DATABASE DEVELOPMENT WORKFLOW                   │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│  1. SCHEMA         2. MODEL           3. MIGRATION          │
│     REVIEW            DESIGN             CREATION           │
│  ┌──────────┐      ┌──────────┐      ┌──────────┐          │
│  │ Analyze  │ ──── │ Define   │ ──── │ Generate │          │
│  │ Design   │      │ Classes  │      │ Scripts  │          │
│  └──────────┘      └──────────┘      └──────────┘          │
│       │                 │                 │                 │
│       ▼                 ▼                 ▼                 │
│  4. ASSOCIATIONS   5. VALIDATIONS     6. SCOPES/QUERIES    │
│     & CALLBACKS                                             │
│  ┌──────────┐      ┌──────────┐      ┌──────────┐          │
│  │ Define   │ ──── │ Add      │ ──── │ Implement│          │
│  │ Relations│      │ Rules    │      │ Queries  │          │
│  └──────────┘      └──────────┘      └──────────┘          │
│                                                              │
└─────────────────────────────────────────────────────────────┘

Step-by-Step Process

1. **Schema Review**

• Analyze database schema design document
• Understand table relationships and constraints
• Identify naming conventions (Rails defaults)
• Review index requirements

2. **Model Design**

• Create model classes in `app/models/`
• Define attribute accessors
• Add type casting where needed
• Implement concerns for shared behavior

3. **Migration Creation**

• Generate Rails migrations
• Ensure reversibility
• Add indexes and foreign keys
• Include data migrations if needed

4. **Associations & Callbacks**

• Define has_many, belongs_to, has_one
• Configure through associations
• Set up polymorphic associations
• Add lifecycle callbacks

5. **Validations**

• Add presence validations
• Implement format validations
• Create custom validators
• Handle uniqueness constraints

6. **Scopes & Queries**

• Define reusable scopes
• Create query objects for complex queries
• Optimize N+1 with includes/preload
• Implement pagination

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ActiveRecord Implementation

Model Definition Pattern

# app/models/user.rb
class User < ApplicationRecord
  # Associations
  has_many :orders, dependent: :destroy
  has_many :products, through: :orders
  has_one :profile, dependent: :destroy

  # Validations
  validates :email, presence: true,
                    uniqueness: { case_sensitive: false },
                    format: { with: URI::MailTo::EMAIL_REGEXP }
  validates :password_hash, presence: true
  validates :display_name, length: { maximum: 100 }

  # Callbacks
  before_validation :normalize_email
  after_create :send_welcome_email

  # Scopes
  scope :active, -> { where(active: true) }
  scope :recently_created, -> { where('created_at > ?', 7.days.ago) }
  scope :with_orders, -> { includes(:orders).where.not(orders: { id: nil }) }
  scope :ordered_by_recent, -> { order(created_at: :desc) }

  # Enums
  enum :role, { user: 0, admin: 1, moderator: 2 }, prefix: true

  # Instance methods
  def full_name
    "#{first_name} #{last_name}".strip
  end

  def active_orders
    orders.where(status: [:pending, :processing])
  end

  private

  def normalize_email
    self.email = email.downcase.strip if email.present?
  end

  def send_welcome_email
    UserMailer.welcome(self).deliver_later
  end
end

Model with Concerns

# app/models/concerns/timestampable.rb
module Timestampable
  extend ActiveSupport::Concern

  included do
    before_save :set_timestamps
  end

  private

  def set_timestamps
    self.updated_at = Time.current if changed?
    self.created_at ||= Time.current if new_record?
  end
end

# app/models/concerns/soft_deletable.rb
module SoftDeletable
  extend ActiveSupport::Concern

  included do
    default_scope { where(deleted_at: nil) }
    scope :with_deleted, -> { unscope(where: :deleted_at) }
    scope :only_deleted, -> { with_deleted.where.not(deleted_at: nil) }
  end

  def soft_delete
    update(deleted_at: Time.current)
  end

  def restore
    update(deleted_at: nil)
  end

  def deleted?
    deleted_at.present?
  end
end

---

Migrations

Standard Migration

# db/migrate/20240115000000_create_users.rb
class CreateUsers < ActiveRecord::Migration[7.1]
  def change
    create_table :users, id: :uuid do |t|
      t.string :email, null: false, limit: 255
      t.string :password_hash, null: false
      t.string :display_name, limit: 100
      t.integer :role, default: 0, null: false
      t.boolean :active, default