Andrew Rawnsley <ronz@ravensfield.com> writes:
> If I were loony enough to want to make an attempt at a version updater
> (i.e. migrate a 7.4 database to 8.0 without an initdb), any
> suggestions on where to poke first?
pg_upgrade is the way to go IMHO. I would not try to "dust off" the old
shell-script code for it, but start from scratch using the fundamental
ideas. To wit, migrate the schema using pg_dump and reload, then push
the existing data files into place. There are enough low-level details
involved that it's better to do this in C than shell code, but the
concept is sound.
This will not work for the 7.4->8.0 transition in particular, because
the data file format changed (heap tuple header changes). But those
sorts of changes are relatively rare and will probably get rarer
(especially if there's any reason for us to try to avoid 'em). If you
start now you might have a credible implementation in time for 8.0->8.1
...
regards, tom lane