Add option to be notified when a followed user posts (#13546)

* Add bell button

Fix #4890

* Remove duplicate type from post-deployment migration

* Fix legacy class type mappings

* Improve query performance with better index

* Fix validation

* Remove redundant index from notifications

1 files changed, 15 insertions, 0 deletions

diff --git a/db/post_migrate/20200917222734_remove_index_notifications_on_account_activity.rb b/db/post_migrate/20200917222734_remove_index_notifications_on_account_activity.rb
new file mode 100644
index 000000000..cb7f78e53
--- /dev/null
+++ b/db/post_migrate/20200917222734_remove_index_notifications_on_account_activity.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class RemoveIndexNotificationsOnAccountActivity < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def up
+    remove_index :notifications, name: :account_activity
+    remove_index :notifications, name: :index_notifications_on_account_id_and_id
+  end
+
+  def down
+    add_index :notifications, [:account_id, :activity_id, :activity_type], unique: true, name: 'account_activity', algorithm: :concurrently
+    add_index :notifications, [:account_id, :id], order: { id: :desc }, algorithm: :concurrently
+  end
+end