DEV: Migrate user_badges#notification_id to bigint (#28546)

The `notifications.id` has been migrated to bigint in previous commit
799a45a291. This commit migrates one of
the related columns, `user_badges.notification_id`, to `bigint`.

app/models/user_badge.rb

@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
 class UserBadge < ActiveRecord::Base
+  self.ignored_columns = [
+    :old_notification_id, # TODO: Remove when column is dropped. At this point, the migration to drop the column has not been writted.
+  ]
+
   belongs_to :badge
   belongs_to :user
   belongs_to :granted_by, class_name: "User"
@@ -120,11 +124,11 @@ end
 #  granted_at      :datetime         not null
 #  granted_by_id   :integer          not null
 #  post_id         :integer
-#  notification_id :integer
 #  seq             :integer          default(0), not null
 #  featured_rank   :integer
 #  created_at      :datetime         not null
 #  is_favorite     :boolean
+#  notification_id :bigint
 #
 # Indexes
 #

db/migrate/20240826121505_add_big_int_user_badges_notification_id.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+class AddBigIntUserBadgesNotificationId < ActiveRecord::Migration[7.0]
+  def up
+    # Create new column
+    execute "ALTER TABLE user_badges ADD COLUMN new_notification_id BIGINT"
+
+    # Mirror new `notification_id` values to `new_notification_id`
+    execute <<~SQL.squish
+      CREATE FUNCTION mirror_user_badges_notification_id()
+      RETURNS trigger AS
+      $$
+      BEGIN
+        NEW.new_notification_id = NEW.notification_id;
+        RETURN NEW;
+      END;
+      $$
+      LANGUAGE plpgsql
+    SQL
+
+    execute <<~SQL.squish
+      CREATE TRIGGER user_badges_new_notification_id_trigger BEFORE INSERT ON user_badges
+      FOR EACH ROW EXECUTE PROCEDURE mirror_user_badges_notification_id()
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

db/migrate/20240826121506_copy_user_badges_notification_id_values.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class CopyUserBadgesNotificationIdValues < ActiveRecord::Migration[7.0]
+  disable_ddl_transaction!
+
+  def up
+    min_id, max_id = execute("SELECT MIN(id), MAX(id) FROM user_badges")[0].values
+    batch_size = 10_000
+
+    (min_id..max_id).step(batch_size) { |start_id| execute <<~SQL.squish } if min_id && max_id
+        UPDATE user_badges
+        SET new_notification_id = notification_id
+        WHERE id >= #{start_id} AND id < #{start_id + batch_size} AND notification_id IS NOT NULL AND new_notification_id IS NULL
+      SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

db/migrate/20240826121507_swap_big_int_user_badges_notification_id.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class SwapBigIntUserBadgesNotificationId < ActiveRecord::Migration[7.0]
+  def up
+    # Necessary to rename and drop columns
+    Migration::SafeMigrate.disable!
+
+    # Drop trigger and function used to replicate new values
+    execute "DROP TRIGGER user_badges_new_notification_id_trigger ON user_badges"
+    execute "DROP FUNCTION mirror_user_badges_notification_id()"
+
+    # Swap columns
+    execute "ALTER TABLE user_badges RENAME COLUMN notification_id TO old_notification_id"
+    execute "ALTER TABLE user_badges RENAME COLUMN new_notification_id TO notification_id"
+
+    # Keep old column and mark it as read only
+    Migration::ColumnDropper.mark_readonly(:user_badges, :old_notification_id)
+  ensure
+    Migration::SafeMigrate.enable!
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end