Re: optimize file transfer in pg_upgrade

On Tue, Mar 18, 2025 at 01:50:10PM -0400, Andres Freund wrote:
> On 2025-03-18 12:47:01 -0500, Nathan Bossart wrote:
>> On Tue, Mar 18, 2025 at 01:37:02PM -0400, Andres Freund wrote:
>> > - Do we need a new old cluster for each of the modes? That seems like wasted
>> >   time?  I guess it's required for --link...
>> 
>> It'll also be needed for --swap.  We could optionally save the old cluster
>> for a couple of modes if we really wanted to.  *shrug*
> 
> Don't worry about it, I think the template initdb stuff should make it cheap enough...

Cool.  I realize now why there's poor coverage for pg_upgrade with
tablespaces: you can't upgrade between the same version with tablespaces
(presumably due to the version-specific subdirectory conflict).  I don't
know if the regression tests leave around any tablespaces for the
cross-version pg_upgrade tests, but that's probably the best we can do at
the moment.

For now, here's a new version of the test with a rewritten table.  I also
tried to fix the expected error regex to handle some of the other error
messages for unsupported modes (as revealed by cfbot).

-- 
nathan