we found old and wrong entries as well in our observium database.
1. When replacing a switch and rediscovering the device, the new details like "entPhysicalDescr" and Serialnumber will be added, but the old details will stay in the database. 
2. after our last replacement, even the adding of the new details seems not be happend.
how can we force the full rediscover without deleting and adding as a new device (we want to keep older metrics and graphs) and of course, cleaning up orphaned entries in the database

I added two scrennshots from an DB export