Migration of a MySQL database fails in Plesk: Unknown collation: 'utf8mb4_unicode_520_ci'

Symptoms

• Unable to migrate a database. The following error is displayed in Plesk:

  PLESK_INFO: Failed to copy content of database 'wordpress_v'
  Migration tools tried to perform operation in 1 attempts: Restoration of MySQL database failed. Most probable reason:
  
  Target MySQL server does not contain necessary character set.
  Most likely it is required to have at least MySQL 5.5 to restore such database.
  ...
  Here is the original error message reported by MySQL client when restoring the database:
  ERROR 1273 (HY000) at line 213: Unknown collation: 'utf8mb4_unicode_520_ci'

• The collation mentioned in the error message is not available in MySQL on the destination server:

  # plesk db -e "show collation" | grep utf8mb4_unicode_520_ci
  #

Cause

On the target server, MySQL can not install the required collation.

Resolution

Apply one of the following solutions:

• Upgrade MariaDB to version 10.1 or 10.2 on the destination server. For instructions, visit this KB article.

• Migrate the subscription to the destination server with the same MySQL version as on the source server.