Re: Major upgrade of PostgreSQL and MySQL

________________________________
From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Ivan Voras <ivoras(at)freebsd(dot)org>; pgsql-general(at)postgresql(dot)org
Sent: Friday, September 13, 2013 9:58 PM
Subject: Re: [GENERAL] Major upgrade of PostgreSQL and MySQL

>> * Ivan Voras (ivoras(at)freebsd(dot)org) wrote:
>>> If I read the documentation correctly
>>> (http://www.postgresql.org/docs/9.3/static/pgupgrade.html), it needs
>>> oldbindir and newbindir arguments pointing to the directories of
>>> PostgreSQL executables for the old and new versions, making it basically
>>> unusable for upgrading systems which are maintained with packages
>>> instead of individually compiling & installing custom versions of
>>> PostgreSQL, right? (except possibly Debian which may allow multiple pg
>>> versions to be installed, I haven't tried it).
>
>> Uhm, don't basically all Debian-based and RedHat-based distributions
>> support having multiple major versions installed concurrently?  It's a
>> pretty reasonable thing to need and, imv anyway, all packaging of PG
>> should support it.
>
>In Red Hat's own packaging, you should temporarily install the
>postgresql-upgrade RPM, which contains pg_upgrade as well as a copy
>of the previous-generation postmaster.  If you use Devrim's packages,
>I think he more nearly follows the Debian approach.  Either way, if
>a packager has failed to allow pg_upgrade to be usable within his
>package set(s), it's a packaging error that you should complain
>about.
>
>

The problem of pg_upgrade is that it needed to hold two set of databases data in the server.
This is not be desirable (very slow) or possible (space limitation) for database with huge data.

For example, if the old version is already using over 50% of the mount point.
The new database may not have enough disk space for the upgrading.

Please correct me if I am wrong.

Thanks,
Patrick