by WhiteRider » Fri Sep 06, 2013 3:18 am
Yes, older databases can't be read by newer versions of PostgreSQL (e.g. an 8.3 database can't be read by 9.0) unless you make a backup in 8.3 and restore in 9.0.
Installing another version of PostgreSQL shouldn't cause any problems, although I'd suggest using to a different port number (e.g. 5483 for 8.3). If you use the same port number again then you will have to be very careful to stop one service before you start the other.