Create RelatedContent model

app/models/related_content.rb

@@ -0,0 +1,11 @@
+class RelatedContent < ActiveRecord::Base
+  belongs_to :parent_relationable, polymorphic: true
+  belongs_to :child_relationable, polymorphic: true
+
+  validates :parent_relationable_id, presence: true
+  validates :parent_relationable_type, presence: true
+  validates :child_relationable_id, presence: true
+  validates :child_relationable_type, presence: true
+  validates :parent_relationable_id, uniqueness: { scope: [:parent_relationable_type, :child_relationable_id, :child_relationable_type] }
+
+end

db/migrate/20171127171925_create_related_content.rb

@@ -0,0 +1,12 @@
+class CreateRelatedContent < ActiveRecord::Migration
+  def change
+    create_table :related_contents do |t|
+      t.references :parent_relationable, polymorphic: true, index: { name: 'index_related_contents_on_parent_relationable' }
+      t.references :child_relationable, polymorphic: true, index: { name: 'index_related_contents_on_child_relationable' }
+      t.references :related_content, index: { name: 'opposite_related_content' }
+      t.timestamps
+    end
+
+    add_index :related_contents, [:parent_relationable_id, :parent_relationable_type, :child_relationable_id, :child_relationable_type], name: "unique_parent_child_related_content", unique: true, using: :btree
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171115164152) do
+ActiveRecord::Schema.define(version: 20171127171925) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -851,6 +851,21 @@ ActiveRecord::Schema.define(version: 20171115164152) do
   add_index "proposals", ["title"], name: "index_proposals_on_title", using: :btree
   add_index "proposals", ["tsv"], name: "index_proposals_on_tsv", using: :gin
 
+  create_table "related_contents", force: :cascade do |t|
+    t.integer  "parent_relationable_id"
+    t.string   "parent_relationable_type"
+    t.integer  "child_relationable_id"
+    t.string   "child_relationable_type"
+    t.integer  "related_content_id"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
+  add_index "related_contents", ["child_relationable_type", "child_relationable_id"], name: "index_related_contents_on_child_relationable", using: :btree
+  add_index "related_contents", ["parent_relationable_id", "parent_relationable_type", "child_relationable_id", "child_relationable_type"], name: "unique_parent_child_related_content", unique: true, using: :btree
+  add_index "related_contents", ["parent_relationable_type", "parent_relationable_id"], name: "index_related_contents_on_parent_relationable", using: :btree
+  add_index "related_contents", ["related_content_id"], name: "opposite_related_content", using: :btree
+
   create_table "settings", force: :cascade do |t|
     t.string "key"
     t.string "value"

spec/factories.rb

@@ -882,4 +882,7 @@ LOREM_IPSUM
     end
   end
 
+  factory :related_content do
+  end
+
 end