fix N+1 queries in AccountsController

fixes CNVS-15391

test plan: accounts api sanity check

Change-Id: I6c218ea92aec63bd3ef52072b5e9b687aeb0c886
Reviewed-on: https://gerrit.instructure.com/40840
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/controllers/accounts_controller.rb

@@ -116,6 +116,7 @@ class AccountsController < ApplicationController
         else
           @accounts = []
         end
+        Account.send(:preload_associations, @accounts, [:root_account])
         render :json => @accounts.map { |a| account_json(a, @current_user, session, params[:includes] || []) }
       end
     end
@@ -177,6 +178,7 @@ class AccountsController < ApplicationController
     @accounts = Api.paginate(@accounts, self, api_v1_sub_accounts_url,
                              :total_entries => recursive ? nil : @accounts.count)
 
+    Account.send(:preload_associations, @accounts, [:root_account, :parent_account])
     render :json => @accounts.map { |a| account_json(a, @current_user, session, []) }
   end
 
@@ -280,6 +282,7 @@ class AccountsController < ApplicationController
 
     @courses = Api.paginate(@courses, self, api_v1_account_courses_url)
 
+    Course.send(:preload_associations, @courses, [:account, :root_account])
     render :json => @courses.map { |c| course_json(c, @current_user, session, [], nil) }
   end
 

app/models/account.rb

@@ -498,9 +498,11 @@ class Account < ActiveRecord::Base
   end
 
   def default_storage_quota
-    read_attribute(:default_storage_quota) ||
-      (self.parent_account.default_storage_quota rescue nil) ||
-      Setting.get('account_default_quota', 500.megabytes.to_s).to_i
+    Rails.cache.fetch(['default_storage_quota', self].cache_key) do
+      read_attribute(:default_storage_quota) ||
+        (self.parent_account.default_storage_quota rescue nil) ||
+        Setting.get('account_default_quota', 500.megabytes.to_s).to_i
+    end
   end
 
   def default_storage_quota_mb