this pops up after the last update from kde-testing repo, where some qt6 packages are updatet. I started kmail from command line and that gives me a org.kde.pim.akonadi_search_pim: Xapian Database corrupted error. So it seems to be a database issue. I took a look at akonadictl, search instance is running. So I think there is a xapian database which has replaced (??) the akonadi database for mail searches… I want to perform xapian-check but that wants to know the location of the database. I have looked but no success. I think i is somewhere in the users home directory… My first try would be to check xapian database (if I know its location). and hope that fixes the issue. If not, maybe a complete rebuild of the kmail search database can fix this (is that possible?) Or any other helpful hint?
Use the main repos unless you want to deal with bugs and maybe report to the dev/package manager, its called testing cos it may not work as expected
Very useful hint 
I know what “testing” means. And that is what I am doing: I test. And there is an issue which can - but must not be - related to “testing”. But if or if not: I want to understand what is going wrong and how I can fix it.
Which is why if you read all I wrote to report upstream either to the arch package manager or to the actual dev, yes I was being a bit cheeky but only in jest mate
Update:
This issue is not related to testing/unstable ! It is only at one of 5 PCs which are running nearly the same software. So it is a corrupted akonadi database “by chance”.
I have deleted all files in ~/.local/share/akonadi/search_db/email while akonadi is stopped and then started akonadi again. Now search in all emails which are newer than the rebuild date works fine, but all emails which are older are ignored. Is there a possibility to start rebuild process of this parrticular database from the beginning?