Remove n+1 query on 'assigned' view column in SP#index

app/controllers/service_packs_controller.rb

@@ -25,6 +25,10 @@ class ServicePacksController < ApplicationController
       wildcard_sanitized_name = "%#{ActiveRecord::Base.send(:sanitize_sql_like, params[:name], -'!')}%"
       @service_packs = @service_packs.where(-"name LIKE ?", wildcard_sanitized_name)
     end
+    # to remove N+1 query 'EXISTS'
+    for_added_column = Assign.active.where(-'service_pack_id = service_packs.id').to_sql
+    @service_packs = @service_packs.select(-'service_packs.*',
+                                           "(CASE WHEN EXISTS (#{for_added_column}) THEN 1 ELSE 0 END) AS assigned")
   end
 
   def new

app/views/service_packs/index.html.erb

@@ -67,7 +67,7 @@
       <td><%= sp.expired_date %></td>
       <td><%= sp.threshold1 %></td>
       <td><%= sp.threshold2 %></td>
-      <td><%= (sp.assigned? ? -'&#x2714' : -'').html_safe %></td>
+      <td><%= (sp.assigned == 1 ? -'&#x2714' : -'').html_safe %></td>
     </tr>
   <% end %>