Add Polymorphism to Broadcasts (Part 1) (#9231) [deploy]

* Add polymorphism to Broadcasts table
  - Adds a broadcastable_id column to Broadcasts
  - Adds a broadcastable_type column to Broadcasts

* Create Announcements and Welcome Notifications tables
  - Adds an Announcements table
  - Adds a Welcome Notifications table
  - Adds timestamps to both tables
  - Adds banner_style column to Announcements table

* Adds Announcement and Welcome Notification models
  - Adds an Announcement model in prep for polymorphism
  - Adds a WelcomeNotification model in prep for polymorphism

* Add data_update script to backfill type_of column for Broadcasts

* Add unique index on broadcastable_type and broadcastable_id on the Broadcasts table

* Add update! to the data_update script to backfill broadcastable_type

app/models/announcement.rb

@@ -0,0 +1,2 @@
+class Announcement < ApplicationRecord
+end

app/models/welcome_notification.rb

@@ -0,0 +1,2 @@
+class WelcomeNotification < ApplicationRecord
+end

db/migrate/20200707170245_add_polymorphism_to_broadcasts.rb

@@ -0,0 +1,6 @@
+class AddPolymorphismToBroadcasts < ActiveRecord::Migration[6.0]
+  def change
+    add_column :broadcasts, :broadcastable_id, :integer
+    add_column :broadcasts, :broadcastable_type, :string
+  end
+end

db/migrate/20200707173316_create_announcements.rb

@@ -0,0 +1,8 @@
+class CreateAnnouncements < ActiveRecord::Migration[6.0]
+  def change
+    create_table :announcements do |t|
+      t.string :banner_style
+      t.timestamps
+    end
+  end
+end

db/migrate/20200707173524_create_welcome_notifications.rb

@@ -0,0 +1,7 @@
+class CreateWelcomeNotifications < ActiveRecord::Migration[6.0]
+  def change
+    create_table :welcome_notifications do |t|
+      t.timestamps
+    end
+  end
+end

db/migrate/20200710174257_add_index_to_broadcasts.rb

@@ -0,0 +1,7 @@
+class AddIndexToBroadcasts < ActiveRecord::Migration[6.0]
+  disable_ddl_transaction!
+
+  def change
+    add_index :broadcasts, %i[broadcastable_type broadcastable_id], unique: true, algorithm: :concurrently
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_07_06_184804) do
+ActiveRecord::Schema.define(version: 2020_07_10_174257) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -58,6 +58,12 @@ ActiveRecord::Schema.define(version: 2020_07_06_184804) do
     t.index ["visit_token"], name: "index_ahoy_visits_on_visit_token", unique: true
   end
 
+  create_table "announcements", force: :cascade do |t|
+    t.string "banner_style"
+    t.datetime "created_at", precision: 6, null: false
+    t.datetime "updated_at", precision: 6, null: false
+  end
+
   create_table "api_secrets", force: :cascade do |t|
     t.datetime "created_at", null: false
     t.string "description", null: false
@@ -293,11 +299,14 @@ ActiveRecord::Schema.define(version: 2020_07_06_184804) do
     t.datetime "active_status_updated_at"
     t.string "banner_style"
     t.text "body_markdown"
+    t.integer "broadcastable_id"
+    t.string "broadcastable_type"
     t.datetime "created_at"
     t.text "processed_html"
     t.string "title"
     t.string "type_of"
     t.datetime "updated_at"
+    t.index ["broadcastable_type", "broadcastable_id"], name: "index_broadcasts_on_broadcastable_type_and_broadcastable_id", unique: true
     t.index ["title", "type_of"], name: "index_broadcasts_on_title_and_type_of", unique: true
   end
 
@@ -1326,6 +1335,11 @@ ActiveRecord::Schema.define(version: 2020_07_06_184804) do
     t.index ["user_id"], name: "index_webhook_endpoints_on_user_id"
   end
 
+  create_table "welcome_notifications", force: :cascade do |t|
+    t.datetime "created_at", precision: 6, null: false
+    t.datetime "updated_at", precision: 6, null: false
+  end
+
   add_foreign_key "api_secrets", "users", on_delete: :cascade
   add_foreign_key "audit_logs", "users"
   add_foreign_key "badge_achievements", "badges"

lib/data_update_scripts/20200708163323_backfill_broadcastable_type_for_broadcasts.rb

@@ -0,0 +1,9 @@
+module DataUpdateScripts
+  class BackfillBroadcastableTypeForBroadcasts
+    def run
+      Broadcast.where(broadcastable_type: nil).each do |cast|
+        cast.update!(broadcastable_type: broadcast.type_of)
+      end
+    end
+  end
+end