Admin dashboard: do a fancier query to avoid n+1 in region user counts

LauraKirby · Apr 1, 2017 · b45d06e · b45d06e
1 parent d29a664
commit b45d06e
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/app/controllers/admin_pages_controller.rb b/app/controllers/admin_pages_controller.rb
@@ -17,6 +17,15 @@ def admin_dashboard
       group(:provider).
       order('count(*)')
 
+    regions_users_count = <<~SQL
+      SELECT COUNT(*)
+      FROM regions_users
+      WHERE region_id = regions.id
+    SQL
+    @region_user_counts = Region.
+      select("name, (#{regions_users_count}) as count").
+      order('count')
+
     @spammers = User.where(spammer: true)
     @spam_events = Event.where(spam: true)
   end

diff --git a/app/views/admin_pages/admin_dashboard.html.erb b/app/views/admin_pages/admin_dashboard.html.erb
@@ -96,10 +96,10 @@
       </tr>
       </thead>
       <tbody>
-      <% Region.all.each do |region| %>
+      <% @region_user_counts.each do |row| %>
         <tr>
-          <td><%= region.name %></td>
-          <td><%= region.users.count %></td>
+          <td><%= row.name %></td>
+          <td><%= row.count %></td>
         </tr>
       <% end %>
       </tbody>