Improve performance of users/show

app/models/following.rb

@@ -4,12 +4,13 @@
 #
 # Table name: followings
 #
-#  id            :integer          not null, primary key
-#  submission_id :integer
-#  user_id       :integer
-#  read          :boolean
-#  created_at    :datetime         not null
-#  kind          :integer          default(NULL)
+#  id                 :integer          not null, primary key
+#  submission_id      :integer
+#  user_id            :integer
+#  read               :boolean
+#  created_at         :datetime         not null
+#  kind               :integer          default(NULL)
+#  submission_user_id :integer
 #
 class Following < ActiveRecord::Base
 
@@ -21,10 +22,22 @@ class Following < ActiveRecord::Base
 
   belongs_to :submission
   belongs_to :user
+  belongs_to :submission_user, class_name: "User" # Could be avoided, but to go faster in users/show
 
   # VALIDATIONS
 
   validates :user_id, uniqueness: { scope: :submission_id }
   validates :kind, presence: true
+
+  # BEFORE, AFTER
+
+  before_validation :set_submission_user_id
+
+  # Automatically compute submission_user_id
+  def set_submission_user_id
+    unless self.submission.nil?
+      self.submission_user = self.submission.user
+    end
+  end
 
 end

app/models/globalstatistic.rb

@@ -24,8 +24,11 @@ class Globalstatistic < ActiveRecord::Base
   # Get the only one row of this table
   def self.get
     statistic = Globalstatistic.first
-    return statistic unless statistic.nil?
-    return Globalstatistic.create
+    if statistic.nil?
+      statistic = Globalstatistic.create
+      statistic.update_all
+    end
+    return statistic
   end
 
   # Recompute all statistics from scratch

app/models/user.rb

@@ -235,7 +235,7 @@ def num_notifications_new(levels)
 
   # Gives the number of submissions with a new comment to read
   def num_notifications_update
-    return followed_submissions.where(followings: { read: false }).count
+    return followings.where(:read => false).count
   end
 
   # Gives the "level" of the user

app/views/users/show.html.erb

@@ -6,7 +6,7 @@
   <% actualrating = @user.rating %>
   <% if actualrating > 0 %>
     <% rank = User.where("rating > ? AND admin = ? AND active = ?", actualrating, false, true).count + 1 %>
-    <% num_users = User.where("rating > 0 AND admin = ? AND active = ?", false, true).count %>
+    <% num_users = Globalstatistic.get.nb_ranked_users %>
     <% rank_centile = (rank == 1 ? 100 : (100.0 * (num_users - rank + 1) / num_users).round(1)) %>
   <% end %>
   <% niveau = @user.level %>
@@ -548,7 +548,7 @@
   <div class="pe-2 pb-2" style="padding-left:20px;">
     <%= @user.name %> s'est inscrit<%= "e" if @user.sex == 1 %> sur Mathraining le <span class="user_color"><%= write_date_only(@user.created_at) %></span>.
     <% if nb_p >= 3 %>
-      <% followings = Following.joins(:submission).includes(:user).where("submissions.user_id = ?", @user.id).group("followings.user_id").select("count(followings.id) AS num_corrections, followings.user_id").order("num_corrections DESC, followings.user_id ASC").to_a %>
+      <% followings = Following.includes(:user).where(:submission_user => @user, :kind => [:first_corrector, :other_corrector]).group(:user_id).select("count(id) AS num_corrections, user_id").order("num_corrections DESC, user_id ASC").to_a %>
       <% if followings.size > 0 %>
         <% tot_num_corr = followings.sum{|f| f.num_corrections} %>
         <% num_correctors_to_show = [3, followings.size].min %>

db/migrate/20241019083617_add_submission_user_id_to_followings.rb

@@ -0,0 +1,10 @@
+class AddSubmissionUserIdToFollowings < ActiveRecord::Migration[7.1]
+  def change
+    add_column :followings, :submission_user_id, :integer
+    add_index :followings, :submission_user_id
+
+    up_only do
+      execute("UPDATE followings f SET submission_user_id = s.user_id FROM submissions s WHERE s.id = f.submission_id")
+    end
+  end
+end

spec/models/following_spec.rb

@@ -2,12 +2,13 @@
 #
 # Table name: followings
 #
-#  id            :integer          not null, primary key
-#  submission_id :integer
-#  user_id       :integer
-#  read          :boolean
-#  created_at    :datetime         not null
-#  kind          :integer          default(NULL)
+#  id                 :integer          not null, primary key
+#  submission_id      :integer
+#  user_id            :integer
+#  read               :boolean
+#  created_at         :datetime         not null
+#  kind               :integer          default(NULL)
+#  submission_user_id :integer
 #
 require "spec_helper"