Cleanup invalid likes without target

db/migrate/20170914202650_cleanup_invalid_likes.rb

+# frozen_string_literal: true
+
+class CleanupInvalidLikes < ActiveRecord::Migration[5.1]
+  class Like < ApplicationRecord
+  end
+
+  def up
+    Like.where(target_type: "Post").joins("LEFT OUTER JOIN posts ON posts.id = likes.target_id")
+        .where("posts.id IS NULL").delete_all
+    Like.where(target_type: "Comment").joins("LEFT OUTER JOIN comments ON comments.id = likes.target_id")
+        .where("comments.id IS NULL").delete_all
+  end
+end