From af75360942a4c29fee7babd2bc828a579ec11bcb Mon Sep 17 00:00:00 2001
From: Sam <sam.saffron@gmail.com>
Date: Wed, 10 Sep 2014 23:03:59 +1000
Subject: [PATCH] PERF: reverse index on topic users to speed up join

---
 db/migrate/20140910130155_create_topic_user_index.rb | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 db/migrate/20140910130155_create_topic_user_index.rb

diff --git a/db/migrate/20140910130155_create_topic_user_index.rb b/db/migrate/20140910130155_create_topic_user_index.rb
new file mode 100644
index 00000000000..0f02e645348
--- /dev/null
+++ b/db/migrate/20140910130155_create_topic_user_index.rb
@@ -0,0 +1,6 @@
+class CreateTopicUserIndex < ActiveRecord::Migration
+  def change
+    # seems to be the most effective for joining into topics
+    add_index :topic_users, [:user_id, :topic_id], unique: true
+  end
+end