For more usefulness, we'd need to keep databases more separate from each
other than we do now. Databases would need to have their own transaction
counters, for example. Shared relations would obviously need major
changes for that to work. If we ultimately could separate databases so
that you could take a filesystem copy of a single database, and restore
it to another cluster, then per-database WAL and PITR would work.
I agree to the fact that we can't have a separate WAL per database. Looks like it makes more sense to create a seperate database cluster, instead of adding one more database, if we want to make better use of available horse power and if we don't have cross database queries.
Thanks,
Gokul.