The correct way to get an ad-hoc task to run as the main admin account
is to leave userid as null.
Setting it causes fatal errors if the main admin account is set to
auth: nologin.
Previously, quiz statistics processing happened on a scheduled task.
This task looked for all quizzes with completed attempts, then
determined if those quizzes had a statistics calculation that's newer
than the most recent attempt, then ran the statistics calculation if
needed. It was hard coded to stop processing after 1 hour.
The queries involved in determining which quizzes needed processing
weren't terribly efficient, and combined with the 1 hour limit this made
the statistics unusable on large sites, where they are the most useful.
This converts the scheduled task to an ad-hoc task, and uses an event
observer for mod_quiz\event\attempt_submitted to queue a task when
it is needed. This removes the need for a query to work out what needs
processing, and allows the task processing to be scaled up as needed.
If a quiz had a long job to calculate statstics running, this would
cause pages that may also attempt a recalculation (the statistics report
page or question bank) to load very slowly, and possibly result in a
database deadlock.
This change will firstly prevent the question bank page performing
analysis calculations at all, since these are not required for this
page, which will speed up loading and prevent deadlocks on this page.
Secondly, this adds a lock to the recalcuation process so that it cannot
run twice concurrently. This will present the user with a message to
indicate that it is waiting for a running calculation until it is
complete, and eventually it will timeout with a message and debugging.
In the description of "Quiz attempt reviewed" events the user IDs of
the reviewer (typically the teacher) and the reviewee (typically the
student) were the wrong way round.
Restoring multiple quizzes from a pre-4.0 backup was broken when
the quizzes shared a random question. This is because after the
first quiz created a set reference in place of the random question,
it deleted the question record so it was not there for the second
quiz to use. This change tracks the IDs of random questions so
they can be deleted at the end.
Previously, a set of calculated quiz statistics would only 'last' for
15 minutes. Then they would be considered invalid and not used.
Now, computed statistics are kept indefinitely. Instead, when a new
batch of values are computed for a particular set of settings, older numbers
for the same settings are deleted first. Therefore,
question_stats_cleanup_task is no more.
Previously, when users viewed the question bank, if the quiz statistics
had not already been calculated, we would try to compute them there an then.
This could be very, very slow, leading to session lock problems.
Now, we never try to compute the statistics on the fly. Instead, we rely
on the existing \quiz_statistics\task\recalculate scheduled task to do it.
I cherry-picked this branch from master (because the current 401
had some conflicts). In master, quiz has been moved to quiz_settings,
so that's why the behat test start failing. Using the proper name
fixes it.
This is very similar to MDL-77090, but at the time, I missed that this
also needed to be handled. (Question metadata is, I think, only used
by the quiz 'Try another question like this one' feature.)
