Comment 2 for bug 1949630

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 number=593] with future log sequence number 230324018

2021-11-03 21:58:07 0 [ERROR] InnoDB: Page [page id: space=0, page number=608] log sequence number 233906241 is in the future! Current system log sequence number 224923522.
2021-11-03 21:58:07 0 [ERROR] InnoDB: Your database may be corrupt or you may have copied the InnoDB tablespace but not the InnoDB log files. Please refer to https://mariadb.com/kb/en/library/innodb-recovery-modes/ for information about forcing recovery.
2021-11-03 21:58:07 0 [ERROR] InnoDB: Page [page id: space=0, page number=325] log sequence number 233904823 is in the future! Current system log sequence number 224923522.
2021-11-03 21:58:07 0 [ERROR] InnoDB: Your database may be corrupt or you may have copied the InnoDB tablespace but not the InnoDB log files. Please refer to https://mariadb.com/kb/en/library/innodb-recovery-modes/ for information about forcing recovery.
2021-11-03 21:58:07 0 [ERROR] InnoDB: Page [page id: space=0, page number=609] log sequence number 233906267 is in the future! Current system log sequence number 224923522.
2021-11-03 21:58:07 0 [ERROR] InnoDB: Your database may be corrupt or you may have copied the InnoDB tablespace but not the InnoDB log files. Please refer to https://mariadb.com/kb/en/library/innodb-recovery-modes/ for information about forcing recovery.
2021-11-03 21:58:07 0 [ERROR] InnoDB: invalid undo header offset 0
2021-11-03 21:58:07 0 [Note] InnoDB: Retry with innodb_force_recovery=5
2021-11-03 21:58:07 0 [ERROR] InnoDB: Plugin initialization aborted with error Data structure corruption
2021-11-03 21:58:07 0 [Note] InnoDB: Starting shutdown...
2021-11-03 21:58:08 0 [ERROR] Plugin 'InnoDB' init function returned error.
2021-11-03 21:58:08 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2021-11-03 21:58:08 0 [Note] Plugin 'FEEDBACK' is disabled.
2021-11-03 21:58:08 0 [ERROR] Unknown/unsupported storage engine: innodb
2021-11-03 21:58:08 0 [ERROR] Aborting

TBH I remember the initial error reports being shorter than this and mentioning that there was a complaint about there being only 1 logfile and that something was wrong with logfile ("Only one logfile found") but the error was very vague.

The only event I can recall (apart from the routine update of ~1000 packages after the upgrade to 21.10) was fixing some unresolved dependency to do with open MPI and octave which did something to a few packages (I wasn't paying attention) and probably is unrelated to this).

I tried innodb_force_recovery up to level 3, I understand more than this may cause damage and I know very little about mysql so I'm reluctant to go further without guidance.

If there are other logs that would be useful I'm happy to try to supply.

I'll switch back to the new db_data so I can continue to use my mail on IMAP...

Ta