From bafb67f702dd3f6038436e47f80cd18dec9bc0b3 Mon Sep 17 00:00:00 2001
From: Chris Blanchard <cablanchard@gmail.com>
Date: Sat, 5 Sep 2015 16:23:50 +0100
Subject: [PATCH] Rewrite recent_topic sql to return unique topics on subquery

---
 app/models/topic.rb       | 9 +++++----
 spec/models/topic_spec.rb | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/app/models/topic.rb b/app/models/topic.rb
index 845d87b..ea3cd43 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -43,11 +43,12 @@ class Topic < ActiveRecord::Base
 
   def self.recent_topics
     find_by_sql %q{
-      SELECT DISTINCT topics.*
-        FROM  (SELECT id, topic_id
+      SELECT topics.*
+        FROM  (SELECT max(id) as max_id, topic_id
                 FROM   posts
-                ORDER  BY id DESC
-                LIMIT  20) AS T
+                GROUP  BY topic_id
+                ORDER  BY max_id DESC
+                LIMIT  10) AS T
                INNER JOIN topics
                        ON T.topic_id = topics.id
                INNER JOIN forums
diff --git a/spec/models/topic_spec.rb b/spec/models/topic_spec.rb
index 718315a..592de27 100644
--- a/spec/models/topic_spec.rb
+++ b/spec/models/topic_spec.rb
@@ -31,7 +31,7 @@ describe Topic do
   describe ".recent_topics" do
     it "returns 5 unique, most recently posted topics" do
       topics = []
-      6.times do
+      10.times do
         topic = create :topic
         topics << topic
         3.times { create :post, topic: topic }