I’d like to know if it’s possible to grab only the data from the mariadb database for a few apps and insert that data into a mariadb database of a fresh installation, so that I will have essentially transferred some app data over from an old installation into a fresh one.
For example, I’d like to transfer over only the Calendar and Deck apps’ data to a fresh installation. I think that in theory this should be possible, but I’d like to know how many different tables this may involve for each app. If each app just uses one table, that should be pretty easy to copy into a new mariadb database.
The reason I’d like to do this is because I have a broken installation that broke a few months ago when updating (I think from version 18 to 19, don’t remember exactly) and I didn’t back up the database before running the web updater (It went smoothly so many times I decided to just update without backing up, and this one time I didn’t back up, it broke). I’m not exactly sure what’s broken, but I have reason to think it’s in the database somewhere.
If it’s not too hard to just copy/paste each app’s table from one database to another, this should solve my problem.
I can’t say anything about the Deck app, but the relevant data for calendars is stored in these tables - some of those might have been introduced after Nextcloud 19 (your table prefix might be different from oc_):
As calendardata is spread over several tables and also synchronization status and other information is stored along with the data, I think just directly importing these tables is quite error-prone.
If there are not to many users and calendars and as long as you have access to the database of the broken instance, you could also export the calendardata to *.ics files with calcardbackup and then import the *.ics files to the new instance.