model class UserLog has next to a user_id also a username field. This value is redundant because the username could be retrieved based on the user id. This redundancy adds to database size, but also makes it harder to rename a user via the database. In my case, such a rename for one user was needed after an LDAP database change.
Proposal is to remove the entry and lookup the username when needed (e.g. used in journal filtering) from the User table based on the user id.