PERF: Do not calculate gaps for TopicViewPostsSerializer.

The client doesn't use the gaps results when loading new posts.

app/serializers/post_stream_serializer_mixin.rb

@@ -12,10 +12,18 @@ module PostStreamSerializerMixin
     true
   end
 
+  def include_gaps?
+    true
+  end
+
   def post_stream
     result = { posts: posts }
     result[:stream] = object.filtered_post_ids if include_stream?
-    result[:gaps] = GapSerializer.new(object.gaps, root: false) if object.gaps.present?
+
+    if include_gaps? && object.gaps.present?
+      result[:gaps] = GapSerializer.new(object.gaps, root: false)
+    end
+
     result
   end
 

app/serializers/topic_view_posts_serializer.rb

@@ -12,6 +12,10 @@ class TopicViewPostsSerializer < ApplicationSerializer
     false
   end
 
+  def include_gaps?
+    false
+  end
+
   def include_timeline_lookup?
     false
   end

spec/serializers/topic_view_posts_serializer_spec.rb

@@ -22,5 +22,6 @@ RSpec.describe TopicViewPostsSerializer do
     expect(posts.first["id"]).to eq(post.id)
     expect(body["post_stream"]["stream"]).to eq(nil)
     expect(body["post_stream"]["timeline_lookup"]).to eq(nil)
+    expect(body["post_stream"]["gaps"]).to eq(nil)
   end
 end