On 9 December 2015 at 18:31, Robert Haas <robertmh...@gmail.com> wrote:
> On Mon, Nov 30, 2015 at 12:58 PM, Bruce Momjian <br...@momjian.us> wrote: > > On Mon, Nov 30, 2015 at 10:48:04PM +0530, Masahiko Sawada wrote: > >> On Sun, Nov 29, 2015 at 2:21 AM, Jeff Janes <jeff.ja...@gmail.com> > wrote: > >> > On Tue, Nov 24, 2015 at 3:13 PM, Masahiko Sawada < > sawada.m...@gmail.com> wrote: > >> >> > >> >> Yeah, we need to consider to compute checksum if enabled. > >> >> I've changed the patch, and attached. > >> >> Please review it. > >> > > >> > Thanks for the update. This now conflicts with the updates doesn to > >> > fix pg_upgrade out-of-space issue on Windows. I've fixed (I think) the > >> > conflict in order to do some testing, but I'd like to get an updated > >> > patch from the author in case I did it wrong. I don't want to find > >> > bugs that I just introduced myself. > >> > > >> > >> Thank you for having a look. > > > > I would not bother mentioning this detail in the pg_upgrade manual page: > > > > + Since the format of visibility map has been changed in version 9.6, > > + <application>pg_upgrade</> creates and rewrite new > <literal>'_vm'</literal> > > + file even if upgrading from 9.5 or before to 9.6 or later with link > mode (-k). > > Really? I know we don't always document things like this, but it > seems like a good idea to me that we do so. > Agreed. For me, rewriting the visibility map is a new data loss bug waiting to happen. I am worried that the group is not taking seriously the potential for catastrophe here. I think we can do it, but I think it needs these things * Clear notice that it is happening unconditionally and unavoidably * Log files showing it has happened, action by action * Very clear mechanism for resolving an incomplete or interrupted upgrade process. Which VMs got upgraded? Which didn't? * Ability to undo an upgrade attempt, somehow, ideally automatically by default * Ability to restart a failed upgrade attempt without doing a "double upgrade", i.e. ensure transformation is immutable -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
