Re: Yet another failure mode in pg_upgrade

Bruce Momjian <bruce(at)momjian(dot)us> writes:
> On Mon, Sep 3, 2012 at 10:07:43AM -0400, Tom Lane wrote:
>> It's not necessary, no? The code now gets socket directory right
>> without help.

> Well, the doc comment is:

> + If running check on an old pre-9.1 Unix-like running server, and the
> + old and new servers use different Unix-domain socket directories,
> + use the <option>-O</> option so the new server uses the same socket
> + directory as the old server, and set <envar>PGHOST</> similarly.

> Remember, we can't get the socket directory for pre-9.1 servers.

Yeah, but even if you assume that pg_upgrade needs help for that, this
doc is wrong and overcomplicated. The case that would be problematic
is where the old server is running with a unix_socket_directory that
is not the same as the default built into pg_upgrade's libpq. It is
not necessary (given my patch) that the new server match that socket
directory. What is necessary is that pg_upgrade be able to contact
the old server. I think, but haven't tested, that it's sufficient
to set PGHOST to make that work. The patched code will override
PGHOST for the new cluster anyway, since it will always specify
--host as the new-cluster socket directory.

regards, tom lane