Re: Proposal: Multiversion page api (inplace upgrade)

Tom Lane wrote:
> Another issue is that it might not be possible to update a page for
> lack of space.  Are we prepared to assume that there will never be a
> transformation we need to apply that makes the data bigger?   In such a
> situation an in-place update might be impossible, and that certainly
> takes it outside the bounds of what ReadBuffer can be expected to manage.

Would a possible solution to this be that you could
  1. Upgrade to the newest minor-version of the old release     (which has knowledge of the space requirements of the
 new one).
 
  2. Run some new maintenance command like "vacuum expand" or     "vacuum prepare_for_upgrade" or something that would
split    any too-full pages, leaving only pages with enough space.
 
  3. Only then shutdown the old server and start the     new major-version server.