From 31d41f532eb887f7c79c000bba6110967795a014 Mon Sep 17 00:00:00 2001
From: Sam <sam.saffron@gmail.com>
Date: Fri, 22 Feb 2019 10:37:18 +1100
Subject: [PATCH] PERF: do not include suggested topics when loading new posts

When a new post is triggered via message bus post stream will attempt to load
it, previously the `/topic/TOPIC_ID/posts.json` would unconditionally include
suggested topics, this caused excessive load on the server.

New pattern defaults to exclude suggested and related topics from this API
unless people explicitly ask for suggested.
---
 .../discourse/models/post-stream.js.es6           |  9 +++++++--
 app/controllers/topics_controller.rb              |  8 ++++++--
 lib/topic_view.rb                                 | 15 +++++++++++++--
 spec/requests/topics_controller_spec.rb           | 10 ++++++++++
 4 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/app/assets/javascripts/discourse/models/post-stream.js.es6 b/app/assets/javascripts/discourse/models/post-stream.js.es6
index 8cc53ea0a77..41889985317 100644
--- a/app/assets/javascripts/discourse/models/post-stream.js.es6
+++ b/app/assets/javascripts/discourse/models/post-stream.js.es6
@@ -907,10 +907,13 @@ export default RestModel.extend({
   },
 
   fetchNextWindow(postNumber, asc, callback) {
+    let includeSuggested = !this.get("topic.suggested_topics");
+
     const url = `/t/${this.get("topic.id")}/posts.json`;
     let data = {
       post_number: postNumber,
-      asc: asc
+      asc: asc,
+      include_suggested: includeSuggested
     };
 
     data = _.merge(data, this.get("streamFilters"));
@@ -950,8 +953,10 @@ export default RestModel.extend({
       return Ember.RSVP.resolve([]);
     }
 
+    let includeSuggested = !this.get("topic.suggested_topics");
+
     const url = "/t/" + this.get("topic.id") + "/posts.json";
-    const data = { post_ids: postIds };
+    const data = { post_ids: postIds, include_suggested: includeSuggested };
     const store = this.store;
 
     return ajax(url, { data }).then(result => {
diff --git a/app/controllers/topics_controller.rb b/app/controllers/topics_controller.rb
index 33b0ebecc06..e311798f250 100644
--- a/app/controllers/topics_controller.rb
+++ b/app/controllers/topics_controller.rb
@@ -197,13 +197,17 @@ class TopicsController < ApplicationController
 
   def posts
     params.require(:topic_id)
-    params.permit(:post_ids, :post_number, :username_filters, :filter)
+    params.permit(:post_ids, :post_number, :username_filters, :filter, :include_suggested)
+
+    include_suggested = params[:include_suggested] == "true"
 
     options = {
       filter_post_number: params[:post_number],
       post_ids: params[:post_ids],
       asc: ActiveRecord::Type::Boolean.new.deserialize(params[:asc]),
-      filter: params[:filter]
+      filter: params[:filter],
+      include_suggested: include_suggested,
+      include_related: include_suggested,
     }
 
     fetch_topic_view(options)
diff --git a/lib/topic_view.rb b/lib/topic_view.rb
index 059b111bbc4..f9b29c44440 100644
--- a/lib/topic_view.rb
+++ b/lib/topic_view.rb
@@ -51,6 +51,9 @@ class TopicView
     @post_number = [@post_number.to_i, 1].max
     @page = [@page.to_i, 1].max
 
+    @include_suggested = options.fetch(:include_suggested) { true }
+    @include_related = options.fetch(:include_related) { true }
+
     @chunk_size =
       case
       when @print then TopicView.print_chunk_size
@@ -402,11 +405,19 @@ class TopicView
   end
 
   def suggested_topics
-    @suggested_topics ||= TopicQuery.new(@user).list_suggested_for(topic, pm_params: pm_params)
+    if @include_suggested
+      @suggested_topics ||= TopicQuery.new(@user).list_suggested_for(topic, pm_params: pm_params)
+    else
+      nil
+    end
   end
 
   def related_messages
-    @related_messages ||= TopicQuery.new(@user).list_related_for(topic, pm_params: pm_params)
+    if @include_related
+      @related_messages ||= TopicQuery.new(@user).list_related_for(topic, pm_params: pm_params)
+    else
+      nil
+    end
   end
 
   # This is pending a larger refactor, that allows custom orders
diff --git a/spec/requests/topics_controller_spec.rb b/spec/requests/topics_controller_spec.rb
index c7851de9003..738d17e5724 100644
--- a/spec/requests/topics_controller_spec.rb
+++ b/spec/requests/topics_controller_spec.rb
@@ -1720,6 +1720,9 @@ RSpec.describe TopicsController do
     let(:topic) { post.topic }
 
     it 'returns first post of the topic' do
+      # we need one for suggested
+      create_post
+
       get "/t/#{topic.id}/posts.json"
 
       expect(response.status).to eq(200)
@@ -1727,6 +1730,13 @@ RSpec.describe TopicsController do
       body = JSON.parse(response.body)
 
       expect(body["post_stream"]["posts"].first["id"]).to eq(post.id)
+
+      expect(body["suggested_topics"]).to eq(nil)
+
+      get "/t/#{topic.id}/posts.json?include_suggested=true"
+      body = JSON.parse(response.body)
+
+      expect(body["suggested_topics"]).not_to eq(nil)
     end
 
     describe 'filtering by post number with filters' do