Hey, It depnends on scenario, but there is many use cases that hack data change from somebody with admin privileges could be disaster. That is the place where data history could come with help. Some basic solution would be trigger which writes previous version of record to some other table. Trigger however can be disabled or removed (crazy solution would be to provide pernament triggers and tables which can only be pernamently inserted). Then we have also possibility to modify tablespace directly on disk.
But Postgres has ability to not override records when two concurrent transaction modify data to provide MVCC. So what about pernamently not vacuumable tables. Adding some xid log tables with hash of record on hash on previous hash. I think that would be serious additional advantage for best open source relational databes. Best regards, Marek Mosiewicz
