Re: Planning incompatibilities for Postgres 10.0

On Sat, May 25, 2013 at 10:39:30AM +0100, Simon Riggs wrote:
> There are a number of changes we'd probably like to make to the way
> things work in Postgres. This thread is not about discussing what
> those are, just to say that requirements exist and have been discussed
> in various threads over time.
> 
> The constraint on such changes is that we've decided that we must have
> an upgrade path from release to release.
> 
> So I'd like to make a formal suggestion of a plan for how we cope with this:
> 
> 1. Implement online upgrade in 9.4 via the various facilities we have
> in-progress. That looks completely possible.
> 
> 2. Name the next release after that 10.0 (would have been 9.5). We
> declare now that
> a) 10.0 will support on-line upgrade from 9.4 (only)
> b) various major incompatibilities will be introduced in 10.0 - the
> change in release number will indicate to everybody that is the case
> c) agree that there will be no pg_upgrade patch from 9.4 to 10.0, so
> that we will not be constrained by that

Assuming online upgrade is going to require logical replication, you are
also assuming 2x storage as you need to have a second cluster to perform
the upgrade.  pg_upgrade would still be needed to upgrade a cluster
in-place.

This sounds like, "I created a new tool which does some of what the old
tool does.  Let's break the old tool to allow some unspecified changes I
might want to make."  I consider this thread to be not thought-through,
obviously.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +