[deploy] Add unique indexes to follows - part 7 (#8215)

app/models/follow.rb

@@ -34,7 +34,7 @@ class Follow < ApplicationRecord
   after_create_commit :create_chat_channel
   before_destroy :modify_chat_channel_status
 
-  validates :followable_id, uniqueness: { scope: %i[followable_type follower_id] }
+  validates :followable_id, uniqueness: { scope: %i[followable_type follower_id follower_type] }
   validates :subscription_status, inclusion: { in: %w[all_articles none] }
 
   def self.need_new_follower_notification_for?(followable_type)

db/migrate/20200702143618_add_unique_index_to_follows_followable_follower.rb

@@ -0,0 +1,13 @@
+class AddUniqueIndexToFollowsFollowableFollower < ActiveRecord::Migration[6.0]
+  disable_ddl_transaction!
+
+  def change
+    add_index(
+      :follows,
+      %i[followable_id followable_type follower_id follower_type],
+      unique: true,
+      algorithm: :concurrently,
+      name: :index_follows_on_followable_and_follower
+    )
+  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_06_18_212422) do
+ActiveRecord::Schema.define(version: 2020_07_02_143618) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -564,6 +564,7 @@ ActiveRecord::Schema.define(version: 2020_06_18_212422) do
     t.string "subscription_status", default: "all_articles", null: false
     t.datetime "updated_at"
     t.index ["created_at"], name: "index_follows_on_created_at"
+    t.index ["followable_id", "followable_type", "follower_id", "follower_type"], name: "index_follows_on_followable_and_follower", unique: true
     t.index ["followable_id", "followable_type"], name: "fk_followables"
     t.index ["follower_id", "follower_type"], name: "fk_follows"
   end

spec/models/follow_spec.rb

@@ -5,7 +5,10 @@ RSpec.describe Follow, type: :model do
   let(:user_2) { create(:user) }
 
   describe "validations" do
+    subject { user.follow(user_2) }
+
     it { is_expected.to validate_inclusion_of(:subscription_status).in_array(%w[all_articles none]) }
+    it { is_expected.to validate_uniqueness_of(:followable_id).scoped_to(%i[followable_type follower_id follower_type]) }
   end
 
   it "follows user" do