Performance improvements for user / group overrides for mod assign

Build a Moodle site with large number of user records, about 150 000 users   (In my case there are 570 000 users) Create a course Create two groups Enrol and Add around 100 users into each groups Create an assignment Create assignment override for each group Load the grading page (mod/assign/view.php?action=grading&id=...) The page is loaded really slow (around 1 minutes or more) Apply the patch Reload the page, it should be much faster (depends on the number of users in the course, not the whole site)