On 19.06.2023 15:44, Simon Avery via discuss wrote:
> My questions!
> 
> 1. Am I right that this was a known bug in Mariadb and has been resolved
> with the .14 release?

Yes, we improved the purge thread to try harder to free UNDO records in
MariaDB 10.6.14.

> 2. The .14 release notes mention “InnoDB does not free UNDO after the fix of
> MDEV-30671 (MDEV-31234)” – is the failure to free UNDO logs a likely cause
> for ibdata1 to grow, given that it stores the undo log?

Yes.

> 3. To recover this space, I will need to do a full mysqldump, wipe and
> reimport of the data, correct?

Unfortunately yes. You can avoid that in the future by creating separate
UNDO table spaces. Put this in your my.cnf:

innodb_undo_tablespaces = 3

see
https://mariadb.com/kb/en/innodb-system-variables/#innodb_undo_tablespaces
for a discussion of the value 3.

This will create 3x 10MB table spaces for the UNDO logs. If those will grow
again, you can shrink them:

SET GLOBAL innodb_undo_log_truncate = ON

but make sure to set it back to OFF afterwards and do it only in times of
low database activity because it can have some impact on performance.


HTH
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