One host, one id, injectively: [a-z0-9.-] stays, anything else becomes _<hex>, and _ is outside the kept set, so two hosts never share a database.
[a-z0-9.-]
_<hex>
_
One host, one id, injectively:
[a-z0-9.-]stays, anything else becomes_<hex>, and_is outside the kept set, so two hosts never share a database.