FEATURE: Forced summary mode for megalodon topics.

This is mainly done for performance reasons and megalodon
topics are usually a byproduct of imports where site setting
limits are not respected.

app/models/post.rb

@@ -355,7 +355,7 @@ class Post < ActiveRecord::Base
             SELECT posts.id
             FROM posts
             WHERE posts.topic_id = #{topic_id.to_i}
-            AND post_number = 1
+            AND posts.post_number = 1
           ) UNION
           (
             SELECT p1.id

lib/topic_view.rb

@@ -482,9 +482,9 @@ class TopicView
     @filtered_posts = unfiltered_posts
 
     # Filters
-    if @filter == 'summary'
+    if @filter == 'summary' || force_summary_mode?
       @filtered_posts = @filtered_posts.summary(@topic.id)
-      @contains_gaps = true
+      @contains_gaps = true unless force_summary_mode?
     end
 
     if @best.present?
@@ -572,4 +572,9 @@ class TopicView
   def is_mega_topic?
     @topic.posts_count >= MEGA_TOPIC_POSTS_COUNT
   end
+
+  def force_summary_mode?
+    @force_summary_mode ||=
+      (@topic.closed? && @topic.posts_count >= (MEGA_TOPIC_POSTS_COUNT * 2))
+  end
 end

spec/components/topic_view_spec.rb

@@ -364,6 +364,26 @@ describe TopicView do
       end
     end
 
+    describe 'when a megalodon topic is closed' do
+      it 'should be forced into summary mode without gaps' do
+        begin
+          original_const = TopicView::MEGA_TOPIC_POSTS_COUNT
+          TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
+          TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", 1)
+          SiteSetting.summary_max_results = 2
+          topic.update!(closed: true)
+
+          topic_view = TopicView.new(topic.id, evil_trout)
+
+          expect(topic_view.contains_gaps?).to eq(false)
+          expect(topic_view.posts).to eq([p5])
+        ensure
+          TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
+          TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", original_const)
+        end
+      end
+    end
+
     it "#restricts to correct topic" do
       t2 = Fabricate(:topic)