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, 7 insertions, 0 deletions

diff --git a/db/migrate/20200917222316_add_index_notifications_on_type.rb b/db/migrate/20200917222316_add_index_notifications_on_type.rb
new file mode 100644
index 000000000..9bd23c1d3
--- /dev/null
+++ b/db/migrate/20200917222316_add_index_notifications_on_type.rb
@@ -0,0 +1,7 @@
+class AddIndexNotificationsOnType < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :notifications, [:account_id, :id, :type], order: { id: :desc }, algorithm: :concurrently
+  end
+end