activerecord

class Post < ApplicationRecord
  belongs_to :author, class_name: 'User'
  has_many :comments, dependent: :destroy

  scope :published, -> { where.not(published_at: nil).where('published_at <= ?', Time.current) }
  scope :draft, -> { where(published_at: nil) }

require "csv"

class PeopleCsvStream
  include Enumerable

  HEADERS = %w[id full_name email signed_up_at plan].freeze

Rails.application.configure do
  config.after_initialize do
    Bullet.enable = true
    Bullet.alert = false
    Bullet.bullet_logger = true
    Bullet.console = true

# BAD: N+1 query problem
@users = User.all
@users.each do |user|
  puts user.posts.count  # Fires query for each user!
end

class AddSettingsToAccounts < ActiveRecord::Migration[7.1]
  disable_ddl_transaction!

  def change
    add_column :accounts, :settings, :jsonb, null: false, default: {}

module EmailNormalization
  extend ActiveSupport::Concern

  included do
    attr_accessor :soft_warnings

class Comment < ApplicationRecord
  belongs_to :post, touch: true
  belongs_to :author, class_name: "User"

  validates :body, presence: true, length: { maximum: 10_000 }

class CreateDeadJobs < ActiveRecord::Migration[7.1]
  def change
    create_table :dead_jobs do |t|
      t.string  :jid, null: false
      t.string  :queue, null: false
      t.string  :klass, null: false

class PostsController < ApplicationController
  def index
    posts = Post.for_feed.page(params[:page]).per(25)

    render json: {
      data: posts.map { |post| PostSerializer.new(post).as_json },

class ReportQuery
  SQL = <<~SQL.freeze
    SELECT date_trunc('day', events.created_at) AS day,
           count(*) AS total,
           count(*) FILTER (WHERE events.kind = 'purchase') AS purchases
    FROM events

class Comment < ApplicationRecord
  belongs_to :post
  belongs_to :author, class_name: "User"

  has_rich_text :body

class Tag < ApplicationRecord
  has_many :taggings, dependent: :destroy

  scope :top, ->(limit = 20) {
    joins(:taggings)
      .group(Arel.sql("tags.id"))