Jim,
I wouldn't be so strongly sure about it. We installed postgresql from apt-get. I removed and installed again even.
See version details on this post still.
source.list is bellow:
deb http://archive.ubuntu.com/ubuntu precise main restricted universe
deb http://archive.ubuntu.com/ubuntu precise-updates main restricted universe
deb http://security.ubuntu.com/ubuntu precise-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu precise partner
