I don't recommend this approach for anything in production that you plan to support or maintain, because as already stated it is unsupported and could break at any time.
However... If you really need the historian to update its cache, you can just restart the historian. As in, edit the config on the gateway and save it again. If you watch the logs, you'll see these entries:
which should make it use what you updated in the table.
Or if you want an even less stable solution, you could automate it with this:
But again, not something I'd put in production...