Document MySQL database migration to utf8mb8
Feature #31921 included in 4.1.0 sets utf8mb4 as default encoding for new MySQL databases setups.
In the description, Marius BALTEANU added :
I'll try to create later a Wiki page regarding the steps required to migrate and existing installation or at least some useful links.
There is no documentation explaining how to migrate yet.
#21398 includes a migration script, but people in that thread reported failures with the script.
Updated by Sylvain Faivre over 2 years ago
Sorry I didn't get back to this issue before.
Migrating a MySQL/MariaDB database to utf8mb4 might require a lot of steps, depending on the MySQL or MariaDB release you have.
I actually migrated our Redmine database using the Nextcloud documentation, which thoroughly describes each case.
This documentation can be found at https://docs.nextcloud.com/server/20/admin_manual/configuration_database/mysql_4byte_support.html
I also had to edit the config/database.yml file in Redmine folder, to alter this entry :