From bad6a5142cd103b95a64250b3b6e89539187e279 Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Fri, 22 Jun 2018 10:38:31 +0800
Subject: [PATCH] PERF: Don't include entire post stream when we're loading
 more posts.

---
 .../discourse/models/post-stream.js.es6       |  5 ++--
 .../post_stream_serializer_mixin.rb           |  8 ++++--
 .../topic_view_posts_serializer.rb            |  8 ++++++
 .../topic_view_posts_serializer_spec.rb       | 26 +++++++++++++++++++
 4 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 spec/serializers/topic_view_posts_serializer_spec.rb

diff --git a/app/assets/javascripts/discourse/models/post-stream.js.es6 b/app/assets/javascripts/discourse/models/post-stream.js.es6
index a2a30048314..7b4b27249ea 100644
--- a/app/assets/javascripts/discourse/models/post-stream.js.es6
+++ b/app/assets/javascripts/discourse/models/post-stream.js.es6
@@ -854,13 +854,14 @@ export default RestModel.extend({
     const url = "/t/" + this.get("topic.id") + "/posts.json";
     const data = { post_ids: postIds };
     const store = this.store;
-    return ajax(url, { data }).then(result => {
-      const posts = Ember.get(result, "post_stream.posts");
 
+    return ajax(url, { data }).then(result => {
       if (result.suggested_topics) {
         this.set("topic.suggested_topics", result.suggested_topics);
       }
 
+      const posts = Ember.get(result, "post_stream.posts");
+
       if (posts) {
         posts.forEach(p => this.storePost(store.createRecord("post", p)));
       }
diff --git a/app/serializers/post_stream_serializer_mixin.rb b/app/serializers/post_stream_serializer_mixin.rb
index 26213f059c8..02f9b582cc8 100644
--- a/app/serializers/post_stream_serializer_mixin.rb
+++ b/app/serializers/post_stream_serializer_mixin.rb
@@ -3,14 +3,18 @@ require_dependency 'post_serializer'
 require_dependency 'timeline_lookup'
 
 module PostStreamSerializerMixin
-
   def self.included(klass)
     klass.attributes :post_stream
     klass.attributes :timeline_lookup
   end
 
+  def include_stream?
+    true
+  end
+
   def post_stream
-    result = { posts: posts, stream: object.filtered_post_ids }
+    result = { posts: posts }
+    result[:stream] = object.filtered_post_ids if include_stream?
     result[:gaps] = GapSerializer.new(object.gaps, root: false) if object.gaps.present?
     result
   end
diff --git a/app/serializers/topic_view_posts_serializer.rb b/app/serializers/topic_view_posts_serializer.rb
index 98c6cabff76..b51acf525f3 100644
--- a/app/serializers/topic_view_posts_serializer.rb
+++ b/app/serializers/topic_view_posts_serializer.rb
@@ -8,4 +8,12 @@ class TopicViewPostsSerializer < ApplicationSerializer
     object.topic.id
   end
 
+  def include_stream?
+    false
+  end
+
+  def include_timeline_lookup?
+    false
+  end
+
 end
diff --git a/spec/serializers/topic_view_posts_serializer_spec.rb b/spec/serializers/topic_view_posts_serializer_spec.rb
new file mode 100644
index 00000000000..f69b4080645
--- /dev/null
+++ b/spec/serializers/topic_view_posts_serializer_spec.rb
@@ -0,0 +1,26 @@
+require 'rails_helper'
+
+RSpec.describe TopicViewPostsSerializer do
+  let(:user) { Fabricate(:user) }
+  let(:post) { Fabricate(:post) }
+  let(:topic) { post.topic }
+  let(:topic_view) { TopicView.new(topic, user, post_ids: [post.id]) }
+
+  subject do
+    described_class.new(topic_view,
+      scope: Guardian.new(Fabricate(:admin)),
+      root: false
+    )
+  end
+
+  it 'should return the right attributes' do
+    body = JSON.parse(subject.to_json)
+
+    posts = body["post_stream"]["posts"]
+
+    expect(posts.count).to eq(1)
+    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)
+  end
+end