Speed up senior_delegate computation during transition to user_groups (…

…thewca#8586)

* Speed up senior_delegate computation during transition to user_groups

* Revert region_id association hack

* Add frozen_string_literal comment

WcaOnRails/app/models/user.rb

@@ -132,8 +132,8 @@ def two_factor_enabled?
     delegate: "delegate",
     senior_delegate: "senior_delegate",
   }
-  has_many :subordinate_delegates, class_name: "User", foreign_key: "senior_delegate_id"
-  belongs_to :senior_delegate, -> { where(delegate_status: "senior_delegate").order(:name) }, class_name: "User", optional: true
+  has_many :subordinate_delegates, class_name: "User", foreign_key: "senior_delegate_id", inverse_of: :senior_delegate
+  belongs_to :senior_delegate, -> { where(delegate_status: "senior_delegate").order(:name) }, class_name: "User", optional: true, inverse_of: :subordinate_delegates
 
   validate :wca_id_is_unique_or_for_dummy_account
   def wca_id_is_unique_or_for_dummy_account

WcaOnRails/db/migrate/20231202155158_add_senior_delegate_region_index.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddSeniorDelegateRegionIndex < ActiveRecord::Migration[7.1]
+  def change
+    add_index :users, [:region_id, :delegate_status]
+  end
+end

WcaOnRails/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2023_11_25_061943) do
+ActiveRecord::Schema[7.1].define(version: 2023_12_02_155158) do
   create_table "Competitions", id: { type: :string, limit: 32, default: "" }, charset: "utf8mb4", collation: "utf8mb4_unicode_ci", force: :cascade do |t|
     t.string "name", limit: 50, default: "", null: false
     t.string "cityName", limit: 50, default: "", null: false
@@ -1124,6 +1124,7 @@
     t.string "otp_secret"
     t.index ["delegate_id_to_handle_wca_id_claim"], name: "index_users_on_delegate_id_to_handle_wca_id_claim"
     t.index ["email"], name: "index_users_on_email", unique: true
+    t.index ["region_id", "delegate_status"], name: "index_users_on_region_id_and_delegate_status"
     t.index ["region_id"], name: "index_users_on_region_id"
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
     t.index ["senior_delegate_id"], name: "index_users_on_senior_delegate_id"