diff --git a/db/migrate/20180621013807_add_index_topic_id_percent_rank_on_posts.rb b/db/migrate/20180621013807_add_index_topic_id_percent_rank_on_posts.rb
new file mode 100644
index 00000000000..d7a2f1f81d7
--- /dev/null
+++ b/db/migrate/20180621013807_add_index_topic_id_percent_rank_on_posts.rb
@@ -0,0 +1,9 @@
+class AddIndexTopicIdPercentRankOnPosts < ActiveRecord::Migration[5.2]
+  def up
+    add_index :posts, [:topic_id, :percent_rank], order: { percent_rank: :asc }
+  end
+
+  def down
+    remove_index :posts, [:topic_id, :percent_rank]
+  end
+end