Virtual machine software like VirtualBox allow one to make incremental VM clones. That is data, once "touched" (opened writable), will be copied and stored in the incremental cache of the new clone.
I am searching for the same option for a Postgres DBMS.
How can I setup an incremental database copy, where entries are read from the original database, and touched/modified rows from the local copy?
If not on the DBMS level, how can I emulate such behavior at the file-system/storage level using a separate DBMS instance?
Background: The idea is to utilize the powerful database-server yet without incurring much resource overhead for a staged/developer database-copy.