Document issues related to DDL in MySQL 5.7/MariaDB 10.2

[Geoff Montee]

MySQL 5.7 and MariaDB 10.2 users can see errors like the following when performing a backup while DDL is running concurrently:

[FATAL] InnoDB: An optimized(without redo logging) DDLoperation has been performed. All modified pages may not have been flushed to the disk yet.
    PXB will not be able take a consistent backup. Retry the backup operation

This blog post has a nice description of the problem:

https://www.percona.com/blog/2017/08/08/avoiding-the-an-optimized-without-redo-logging-ddloperation-has-been-performed-error-with-percona-xtrabackup/

But I do not see any mentions of this problem on any of the following documentation pages:

https://www.percona.com/doc/percona-xtrabackup/2.4/known_issues.html

https://www.percona.com/doc/percona-xtrabackup/2.4/faq.html

https://www.percona.com/doc/percona-xtrabackup/2.4/xtrabackup_bin/xbk_option_reference.html

Maybe some of the details from the blog post should be included in the XtraBackup documentation?

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXB-509