Tim Hunt

This was asked in the 'Large scale installations' Matrix chat challen recently. Follow the 'Moodle community' at https://moodledev.io/general/channels#chats to find that channel.

But, the summary is that Valkey is a drop-in replacement. It just works, and various people are already using it.

Note that, while the form of the boiler-plate comment is checked by CodeChecker, it intentionally does not check every single word: https://github.com/moodlehq/moodle-cs/blob/main/moodle/Sniffs/Files/BoilerplateCommentSniff.php#L34

I implemented that originally, at the request of the STACK project, so they could say: https://github.com/maths/moodle-qtype_stack/blob/master/version.php.

I agree that this is probably good practice (but I don't bother in most of my plugins, just because it is easier to copy/paste comments from an existing file and not think about it).

There should be an explanation at https://docs.moodle.org/dev/Quiz_statistics_calculations, but currently equation rendering is broken there, which makes the page not very helpful. (MDLSITE-8046).

The code that computes the statistics is spread over various classes, but if you want to look, https://github.com/moodle/moodle/blob/3e73c33f9920fbb066f2c554fb998af46d4706d8/question/classes/statistics/questions/calculator.php#L37 is probably a reasonable place to start. (And, how that is called from mod/quiz/report/statistics code.)

I think you are seeing an after-effect of MDL-82772, which has now been fixed. At any rate, the error is arising becuase the random questions are messed up and pointing to a category that no longer exists. The fact that displaying this outputs erros is really a sympton, but the but is how did it get like that?

If you can still reproduce this, please let us know the exact steps so we can fix it.

This definitely should not be happening. The values in the questionid column of the question_versions table should be unique. (Why doesn't the DB schema enforce this? I created MDL-85197.)

In the cases where you have several rows in question_versions with the questionid, which questions are those? can deduce how it got like that?