After upgrading from Mageia 7 to Magia 8 I was very surprised to find that Kontact would not start.
When I tried to open Kontact a message window displayed showing that Akonadi server was not starting.
Akonadi stores the data that is shared among the components of Kontact (mail, contact, calendar etc. )
To store the data Akonadi uses MariaDB database server.
I did a lot of internet searching and found that the problem was not with the upgrade to Mageia 8 but with the upgrade to MariaDB that was part of the process.
Many posts suggested that the problem was with the way newer versions of MariaDB define paths using "mariadb" instead of "mysql".
They found solutions by rolling back to an earlier version of MariaDB, running "mariadb-upgrade" and then installing the current version of MariaDB.
Fortunately I found a much simpler solution thanks to a post on an archlinux forum (those folks do great documentation!).
They said that as of MariaDB 10.5 the redo log could no longer be split into multiple files and suggested looking for files like "ib_logfile0" and "ib_logfile1" and renaming them like "ib_logfile0_old" so that there would be only one log file.
--- and it worked like magic ---
In /home/my_user_name/.local/share/akonadi/db_data/
I just renamed the ib_logfile0 to iblogfile0.old then the iblogfile1 disappeared, after a restart I checked using ksysgard and saw that there were now two instances of mysqld running, one for username = my_user_name (with parent = akonadiserver) and the regular one with username = mysql and parent = systemd
I started Kontact from krunner and everything looks good.
Wow! that sure beats a rollback and an upgrade.
I hope this helps anyone who may be having a similar problem after a MariaDB upgrade.