PERF: Preload user options when status is enabled (#28827)

The user option 'hide_profile_and_presence' is necessary to figure out
if the user status has to be displayed or not. In order to avoid N+1s
generated by `include_status?` method, both `user_status` and
`user_option` relations have to be included.

lib/topic_view.rb

@@ -752,8 +752,9 @@ class TopicView
         usernames.flatten!
         usernames.uniq!
 
-        users =
-          User.where(username_lower: usernames).includes(:user_status).index_by(&:username_lower)
+        users = User.where(username_lower: usernames)
+        users = users.includes(:user_option, :user_status) if SiteSetting.enable_user_status
+        users = users.index_by(&:username_lower)
 
         mentions.reduce({}) do |hash, (post_id, post_mentioned_usernames)|
           hash[post_id] = post_mentioned_usernames.map { |username| users[username] }.compact

spec/requests/topics_controller_spec.rb

@@ -2438,6 +2438,25 @@ RSpec.describe TopicsController do
       expect(second_request_queries.count).to eq(first_request_queries.count)
     end
 
+    it "does not result in N+1 queries loading mentioned users" do
+      SiteSetting.enable_user_status = true
+
+      post =
+        Fabricate(
+          :post,
+          raw:
+            "post with many mentions: @#{user.username}, @#{user_2.username}, @#{admin.username}, @#{moderator.username}",
+        )
+
+      queries = track_sql_queries { get "/t/#{post.topic_id}.json" }
+
+      user_statuses_queries = queries.filter { |q| q =~ /FROM "?user_statuses"?/ }
+      expect(user_statuses_queries.size).to eq(2) # for current user and for all mentioned users
+
+      user_options_queries = queries.filter { |q| q =~ /FROM "?user_options"?/ }
+      expect(user_options_queries.size).to eq(1) # for all mentioned users
+    end
+
     context "with registered redirect_to_correct_topic_additional_query_parameters" do
       let(:modifier_block) { Proc.new { |allowed_params| allowed_params << :silly_param } }