Polymorphic conditions

tag.rb

class Tag < ActiveRecord::Base
  validates :name, presence: true, uniqueness: true

  has_many :taggings
  has_many :case_studies, through: :taggings, source: :taggable, source_type: 'CaseStudy'
  has_many :posts, through: :taggings, source: :taggable, source_type: 'Post'
  has_many :events, through: :taggings, source: :taggable, source_type: 'Event'
end

tagging.rb

class Tagging < ActiveRecord::Base
  validates :tag, presence: true
  validates :taggable_id, presence: true
  validates :taggable_type, presence: true

  belongs_to :tag
  belongs_to :taggable, polymorphic: true

  def self.published
    joins_posts.joins_events.joins_case_studies.
      where(
        'posts.published = ? OR events.id IS NOT NULL OR case_studies.id IS NOT NULL',
        true
      )
  end

  def self.chronological
    order('coalesce(posts.published_at, events.start_date, case_studies.created_at) DESC')
  end

  def self.joins_posts
    joins <<-SQL
      LEFT JOIN posts
        ON posts.id = taggings.taggable_id
        AND taggings.taggable_type = 'Post'
    SQL
  end

  def self.joins_events
    joins <<-SQL
      LEFT JOIN events
        ON events.id = taggings.taggable_id
        AND taggings.taggable_type = 'Event'
    SQL
  end

  def self.joins_case_studies
    joins <<-SQL
      LEFT JOIN case_studies
        ON case_studies.id = taggings.taggable_id
        AND taggings.taggable_type = 'CaseStudy'
    SQL
  end
end

tags_controller.rb

class TagsController < ApplicationController
  def show
    @tag = Tag.find(params[:id])
    @taggings = @tag.taggings.published.chronological.page(params[:page])
  end
end

This is a genius solution. You are an amazing SQL engineer. I love you.