Re: pg_upgrade project status

Stephen Frost <sfrost(at)snowman(dot)net> writes:
> * Zdenek Kotala (Zdenek(dot)Kotala(at)Sun(dot)COM) wrote:
>> And very important thing is that you need old version of postgreSQL
>> installed, which is something what packagers does not want. Look on
>> Oracle how does it.

> Just as a counter-point, Debian handles multiple concurrently installed
> versions of PostgreSQL just fine, in large part to specifically deal
> with the smooth migration challenge (though also because we realize
> people may want to continue using the old version while others may want
> to install the new version).

> Not sure if that's something the community wants to encourage other
> packagers to do or if we should look at making it easier to do, but it's
> at least possible and has been done for a pretty large distribution.

The Red Hat/Fedora brigade has also been thinking seriously about that,
though we've not gotten further than thinking yet. Of course, if
pg_upgrade becomes a reality we'd likely stop thinking about it.

IMHO, it would not by any means be a disaster for pg_upgrade to require
a copy of the older-version postmaster. The way I'd foresee packaging
it is to build a separate postgresql-upgrade RPM containing pg_upgrade
itself and a version-N-minus-1 postmaster that gets installed in a
nonstandard location (that pg_upgrade knows about). After you've
finished the upgrade you can remove that RPM and get the extra disk
space back. Most of the possible alternatives mean a *permanent*
disk space hit, because the postmaster will have to contain one-time-use
upgrade code that can't be dropped afterwards.

regards, tom lane