Add index to `notifications.type` and make it non-nullable

db/migrate/20220720190421_add_type_to_notifications.rb

@@ -3,6 +3,7 @@
 class AddTypeToNotifications < ActiveRecord::Migration[6.1]
   def up
     add_column :notifications, :type, :string
+    add_index :notifications, :type
 
     execute "UPDATE notifications SET type = 'Notification::Commented' WHERE target_type = 'Comment'"
     execute "UPDATE notifications SET type = 'Notification::QuestionAnswered' WHERE target_type = 'Answer'"
@@ -14,9 +15,12 @@ class AddTypeToNotifications < ActiveRecord::Migration[6.1]
         AND target_id IN (SELECT id FROM appendables WHERE type = 'Appendable::Reaction' AND parent_type = 'Answer');
     SQUIRREL
     execute "UPDATE notifications SET type = 'Notification::CommentSmiled' WHERE type IS NULL"
+
+    change_column_null :notifications, :type, false
   end
 
   def down
+    remove_index :notifications, :type
     remove_column :notifications, :type
   end
 end

db/schema.rb

@@ -116,9 +116,10 @@ ActiveRecord::Schema.define(version: 2022_07_20_190421) do
     t.boolean "new"
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.string "type"
+    t.string "type", null: false
     t.index ["new"], name: "index_notifications_on_new"
     t.index ["recipient_id"], name: "index_notifications_on_recipient_id"
+    t.index ["type"], name: "index_notifications_on_type"
   end
 
   create_table "profiles", force: :cascade do |t|