Optimize db queries on the front page

Gemfile

@@ -65,6 +65,7 @@ gem 'cancancan'
 gem 'doorkeeper'
 
 # db
+gem 'active_record_union'
 gem 'activerecord-import'
 gem 'arel'
 gem 'aws-sdk-rails'

Gemfile.lock

@@ -43,6 +43,8 @@ GEM
       activemodel (>= 4.1, < 6)
       case_transform (>= 0.2)
       jsonapi-renderer (>= 0.1.1.beta1, < 0.3)
+    active_record_union (1.3.0)
+      activerecord (>= 4.0)
     activejob (5.2.0)
       activesupport (= 5.2.0)
       globalid (>= 0.3.6)
@@ -436,6 +438,7 @@ PLATFORMS
 
 DEPENDENCIES
   active_model_serializers
+  active_record_union
   activerecord-import
   administrate
   api-pagination (= 4.7)

app/models/game.rb

@@ -6,7 +6,7 @@ class Game < ApplicationRecord
 
   validates :name, presence: true
 
-  has_many :categories
+  has_many :categories, dependent: :destroy
   has_many :runs, through: :categories
   has_many :users, -> { distinct }, through: :runs
   has_many :runners, -> { distinct }, through: :runs, class_name: 'User'

app/models/user.rb

@@ -39,7 +39,7 @@ def self.search(term)
 
   # avatar returns the user's avatar, or a default avatar if the user has not set one. It cannot return nil.
   def avatar
-    return "https://splits.io/logo.svg" if read_attribute(:avatar).nil?
+    return 'https://splits.io/logo.svg' if read_attribute(:avatar).nil?
 
     URI.parse(read_attribute(:avatar) || '').tap do |uri|
       uri.scheme = 'https'
@@ -63,9 +63,8 @@ def previous_upload_for(category)
   end
 
   def pbs
-    runs.where(
-      id: categories.map { |category| pb_for(category).id10 } | runs.where(category: nil).pluck(:id)
-    )
+    runs.where.not(category: nil).select('DISTINCT ON (category_id) *').order('category_id, realtime_duration_ms ASC')
+        .union_all(runs.by_category(nil))
   end
 
   def runs?(category)

app/views/runs/index.slim

@@ -9,7 +9,7 @@
       span Splits I/O
   - else
     h2 Splits I/O
-  - if logged_in? && current_user.runs.present?
+  - if logged_in? && current_user.runs.any?
     h5 Want some jelly with these PBs?
   - else
     h5
@@ -20,7 +20,7 @@ article
   .row
     .col-lg-12
       - if logged_in?
-        - if current_user.runs.present?
+        - if current_user.runs.any?
           .card.shadow
             = render partial: 'shared/run_table', locals: { \
               runs: current_user.pbs, \

app/views/shared/_follows.slim

@@ -2,7 +2,9 @@
   h4 Recent PBs By People You Follow
   .card.col-md-6.p-0
     .list-group
-      - Run.includes(:game, :category, :user).where(user: current_user.twitch_followed_users).where.not(games: {name: [nil, ""]}).order('runs.created_at DESC').limit(10).each do |run|
+      - followed_runs = Run.includes(:game, :category, :user).where(user: current_user.twitch_followed_users).where.not(games: {name: [nil, ""]}).order('runs.created_at DESC').limit(10)
+      - user_runs = current_user.pbs.where(category_id: followed_runs.map(&:category_id))
+      - followed_runs.each do |run|
         = link_to(run, class: 'list-group-item list-group-item-action flex-column align-items-start')
           .media
             = image_tag(run.user.avatar, size: '70x70', class: 'mr-3')
@@ -14,8 +16,8 @@
                 = "#{run.game} #{run.category}"
                 div
                   = format_ms(run.duration_ms(Run::REAL))
-                  - if current_user.runs?(run.category)
-                    - user_pb = current_user.pb_for(run.category)
+                  - user_pb = user_runs.detect { |r| r.category_id == run.category_id }
+                  - if user_pb.present?
                     = " ("
                     = pretty_difference(user_pb.duration_ms(Run::REAL), run.duration_ms(Run::REAL))
                     = ")"

app/views/shared/_run_table.slim

@@ -1,7 +1,7 @@
 - description ||= nil
 - cols ||= [:runner, :time, :name, :rival, :uploaded]
 - runs = order_runs(runs).page(params[:page])
-- if runs.empty?
+- if runs.blank?
   center
     i No runs matched!
 - else
@@ -24,7 +24,7 @@
           - if cols.include?(:uploaded)
             th.align-right = th_sorter('Uploaded', 'created_at')
       tbody
-        - runs.includes(:user).each do |run|
+        - runs.includes(:user, :game, :category).each do |run|
           tr id="run_#{run.id36}"
             - if cols.include?(:owner_controls)
               td.align-right
@@ -43,13 +43,13 @@
             - if cols.include?(:rival)
               td.align-right
                 small
-                  - rival = run.user.rival_for(run.category)
-                  - if rival.present? && rival.runs?(run.category)
-                    - rival_run = rival.pb_for(run.category)
+                  - rivalry = run.user.rivalries.includes(:to_user).detect { |r| r.category_id == run.category_id }
+                  - if rivalry.present? && rivalry.to_user.pb_for(run.category).present?
+                    - rival_run = rivalry.to_user.pb_for(run.category)
                     = link_to compare_path(run, rival_run), class: 'run-link stealth-link' do
                       = pretty_difference(run.duration_ms(Run::REAL), rival_run.duration_ms(Run::REAL))
                       '  against
-                      = user_badge(rival)
+                      = user_badge(rivalry.to_user)
                   - elsif run.category.present?
                     = link_to new_rivalry_path(category: run.category)
                       .text-success = icon('fas', 'plus')