Re: Resurrecting pg_upgrade

On Fri, 2003-12-12 at 14:00, Tom Lane wrote:
> Currently the no-table-contents-changes restriction keeps us from
> upgrading from versions older than 7.4 anyway (since type NUMERIC had its
> on-disk representation changed in 7.4).  We could possibly upgrade 7.3
> databases that contain no NUMERIC columns, if we take the hit of
> rebuilding indexes.  But is it worth bothering with?

How limiting is the above?  Does this mean that pg_upgrade will be
rendered invalid if there is an on-disk representation change?  Do we
think we will make it from 7.4 -> 7.5 without on-disk changes?  Do we
think at this point most upgrades will be without on-disk changes?  

Or am I missing something, and pg_upgrade will / can do some magic to
work around on-disk changes?