kmail upgrade to 20.10 mysql corruption / data loss

[SA]

I upgraded from 20.04->21.04-21.10

Once at 21.10 everything seem to work fine (yesterday) but today a massive lot of updates were installed (not unexpected) however during these updates kmail stopped working.

Once I got around to restarting kmail (no change) I discovered akonadi had crashed and would not start again. Much digging around later it seems it is because mysql will not start and much digging around later it looks like the data in db_data is corrupt. Specifically there is something wrong with ib_logfile0 and it seems to expect ib_logfile1 to be present but it isn't.

So at this point I made a copy of this directory and trying loads of different stuff (found on the internet) nothing has fixed it. Deleting ib_logfile0 allows akonadi to start and I have my IMAP accounts but several years worth of mail in my local mail directories has been lost.

I have no idea what has gone wrong. kmail crashed because akonadi crashed. Akonadi crashed during a big bunch of updates after upgrading from 21.04 to 21.10. Prior to the crash it appeared to be running fine on 21.10.

I do not know where to start with recovery of my mail or where the bug belongs or what the bug is only that akonadi borked during updates and it appears I've lost emails as a result.

[I-Cat (i-cat)]

debbug log?

[SA (superaorta)]

Ok - I have a working version based on a new db_data directory (none of my local mail folders exist)- I've stopped akonadi, replaced the db_data with the backup I made _after_ the problem started - I don't have a backup of this prior to the start of the problem.

With the "as it was when the problem occurred db_data" file I get this:

akonadictl start
org.kde.pim.akonadictl: Starting Akonadi Server...
org.kde.pim.akonadictl: done.
eye know:lunesta:93 Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadiserver: Starting up the Akonadi Server...
org.kde.pim.akonadiserver: database server stopped unexpectedly
org.kde.pim.akonadiserver: Database process exited unexpectedly during initial connection!
org.kde.pim.akonadiserver: executable: "/usr/sbin/mysqld"
org.kde.pim.akonadiserver: arguments: ("--defaults-file=/home/matt/.local/share/akonadi/mysql.conf", "--datadir=/home/matt/.local/share/akonadi/db_data/", "--socket=/run/user/1000/akonadi/mysql.socket", "--pid-file=/run/user/1000/akonadi/mysql.pid")
org.kde.pim.akonadiserver: stdout: ""
org.kde.pim.akonadiserver: stderr: "2021-11-03 21:58:07 0 [Note] /usr/sbin/mysqld (mysqld 10.5.12-MariaDB-1build1) starting as process 33257 ...\n"
org.kde.pim.akonadiserver: exit code: 1
org.kde.pim.akonadiserver: process error: "Unknown error"
org.kde.pim.akonadiserver: Failed to remove runtime connection config file
org.kde.pim.akonadiserver: Shutting down AkonadiServer...
org.kde.pim.akonadicontrol: Application '/usr/bin/akonadiserver' exited normally...

It leaves a log file:
head -15 db_data/mysql.err
2021-11-03 21:58:07 0 [Note] InnoDB: Uses event mutexes
2021-11-03 21:58:07 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
2021-11-03 21:58:07 0 [Note] InnoDB: Number of pools: 1
2021-11-03 21:58:07 0 [Note] InnoDB: Using crc32 + pclmulqdq instructions
2021-11-03 21:58:07 0 [Note] mysqld: O_TMPFILE is not supported on /tmp (disabling future attempts)
2021-11-03 21:58:07 0 [Note] InnoDB: Using Linux native AIO
2021-11-03 21:58:07 0 [Note] InnoDB: Initializing buffer pool, total size = 134217728, chunk size = 134217728
2021-11-03 21:58:07 0 [Note] InnoDB: Completed initialization of buffer pool
2021-11-03 21:58:07 0 [Note] InnoDB: Starting crash recovery from checkpoint LSN=224232972,224232972
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page number=490] with future log sequence number 230329228
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page number=489] with future log sequence number 230328945
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page number=488] with future log sequence number 233940779
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page number=379] with future log sequence number 230326976
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page number=594] with future log sequence number 233913459
2021-11-03 21:58:07 0 [Note] InnoDB: Ignoring a doublewrite copy of page [page id: space=0, page numbe...