On Tue, 8 May 2007, Tom Lane wrote:
What Debian has done is set up an arrangement that lets you run two (or more) different PG versions in parallel. Since that's amazingly helpful during a major-PG-version upgrade, most of the other packagers are scheming how to do something similar.
I alluded to that but it is worth going into more detail on for those not familiar with this whole topic. I normally maintain multiple different PG versions in parallel already, mostly using environment variables to switch between them with some shell code. Debian has taken an approach where commands like pg_ctl are wrapped in multi-version/cluster aware scripts, so you can do things like restarting multiple installations more easily than that.
My issue wasn't with the idea, it was with the implementation. When I have my newbie hat on, it adds a layer of complexity that isn't needed for simple installs. And when I have my developer hat on, I found that need to conform to the requirements of that system on top of Debian's already unique install locations and packaging issues just made it painful to build and work with with customized versions of Postgres, compared to distributions that use a relatively simple packaging scheme (like the RPM based RedHat or SuSE).
I hope anyone else working this problem is thinking about issues like this. Debian's approach strikes me as being a good one for a seasoned systems administrator or DBA, which is typical for them. I'd hate to see a change in this area make it more difficult for new users though, as that's already perceived as a PG weakness. I think you can build a layer that adds the capability for the people who need it without complicating things for people who don't.
and if someday you want commercial support for your OS, a Centos->RHEL update will get you there easily.
For those that like to live dangerously, it's also worth mentioning that it's possible to hack this conversion in either direction without actually doing an OS re-install/upgrade just by playing with the packages that are different between the two. So someone who installs CentOS now could swap to RHEL very quickly in a pinch if they have enough cojones to do the required package substitutions.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD
