This changes the cache purge code to select IDs for deletion
first, rather than using a subquery in a DELETE, since this
risks causing a deadlock in MySQL.
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.
We were experiencing problems caused by old stats analysis in our
database, computed when there was a bug, causing fatal errors
when they were displayed. Therefore, this code needs to be robust to that.
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.
PHP before version 8.1 automatically converted to int if the function
parameter (or array key) is expected to be int. PHP 8.1 shows notice in
this case
The versioning changes will require some major changes
in the backup and restore of question bank and its
elements. This change introduces those changes to make
it compatible with the new world of versioning in question
bank. This commit also removes quiz_slots fields and
quiz_slot_tags table.
This commit will also introduce the versioning db
structure and some major changes to the quiz
and quiz attempts for the question, random
question and the view.
This commit implements the behat changes for versioning
in core question and associated locations.
Variants should also be treated like random questions in the sense that
a summary row
should be displayed for them as well.
This commit deals with handling variants.
Also the name of the calculated_random_question_summary class has
changed to
calculated_question_summary to be more generic as the summary row is not
specific to random questions only.
Also removed the protected function too_many_subq_and_or_variant_rows
and the const SUBQ_AND_VARIANT_ROW_LIMIT as they were not being used
anymore.
Part of MDL-62610
Fixed calculated_random_question_summary:get_min_max_of and calculated_random_question_summary:get_min_max_of_sd
functions and added unit tests
Part of MDL-62610
Modified calculated_random_question_summary class so that it can return minimum and maximum
of each attribute of the sub questions it is summarising.
Part of MDL-62610
quiz_question_statistics_stats renamed to question_statistics_calculator
separate class question_statistics used to store calculated stats
and api changed, also code generally cleaned up.
quiz_question_statistics_stats renamed to question_statistics_calculator
separate class question_statistics used to store calculated stats
and api changed, also code generally cleaned up.
Tim Hunt