Optimisation - Saving openTabs in User Preferences fails on courses with many sections

[DocDanouBot]

Dear James,

first of all, thank you for you great add on an the time you invested into making the moodle world a little bit better.

Now I am sitting on a moodle, where the editors have been building a course with hundrets of sections and subelements. As every section has a date in the title, I have to assume, that they are going to extend this long list of sections even further. When we use the format_multitopic we run into an error while executing set_user_preference()

This arrives when moodle tries to save the state of the opened / closed sections due to DB restrictions in the field mdl_user_preferences.value which is a varchar(1333)

We run format_multitopic on the version: 2023072900
and moodle 4.1 . I know that there is a new version of your plugin available (2024051601) , but as I checked the CHANGES.md, this issues has not yet been tackeled, right? Or am I missing something?

We thought of different ways how this problem could be solved: like saving every open / close seperatly for each section or alternativly splitting the long json object into multiple upfollowing entries that have to be concatted. Where each block does not exceed 1333 chars.

Do you think that you will find time in the near future to adress this issue?
Thanks for your reply.

[james-cnz]

Sorry, I don't think I'll address this in the near future. I think this is really a Moodle issue, and I'd prefer to see an attempt made to address it in Moodle before considering working around it in my plugin.

Both the methods you suggest sound plausible to me, and I'm not sure which is the better approach.

Saving the preferences for each section as a separate record seems like the cleaner solution, but would probably involve more reads and writes, take up more space, and be a bigger change. [EDIT: There may be another issue. I'm not sure if there's currently a way to search for preferences that match wild cards through the helper functions. This might make it difficult to delete preferences for sections that have been deleted.]

Splitting the data into several records would probably mostly be simpler. However I think I heard somewhere that there's a a limit to the total size of preferences for a user. If this is the case, and the point was reached where collapsing another section would try to add another record, but fail, then the preferences could be left in an inconsistent state. I think these preferences are written through a helper function, so atomic writes couldn't be used unless the helper function was changed to support it. I guess perhaps the old preferences would need to be remembered, then, in the case of an error, written back.

[katlee890]

Hi!
We also use Multitopic (great plugin, we and our teachers love it!) and have recently had the same error message.

I have already posted a post about it here and hope that the Moodle developers will offer a solution soon:
https://tracker.moodle.org/browse/MDL-78073?focusedCommentId=999738&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel

We have some very large courses with Multitopic with many sections that serve as a knowledge database for everyone. The fact that the error message appears every time a section is expanded is unacceptable.

Best wishes,
Kat

[james-cnz]

This issue has gotten worse in Moodle 4.x due to a regression (see https://moodle.atlassian.net/browse/MDL-86625). Since Moodle 4.5 now only has security support, this is unlikely to be fixed, and the patch would have to be applied manually. Hopefully it is less of an issue in Moodle 5.x, though.