Re: [PoC] pg_upgrade: allow to upgrade publisher node

Hi,

On Thu, Apr 20, 2023 at 05:31:16AM +0000, Hayato Kuroda (Fujitsu) wrote:
> Dear Vignesh,
>
> Thank you for reviewing! PSA new patchset.
>
> > > Additionally, I added a checking functions in 0003
> > > According to pg_resetwal and other functions, the length of
> > CHECKPOINT_SHUTDOWN
> > > record seems (SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort +
> > sizeof(CheckPoint)).
> > > Therefore, the function ensures that the difference between current insert
> > position
> > > and confirmed_flush_lsn is less than (above + page header).

I think that this test should be different when just checking for the
prerequirements (live_check / --check) compared to actually doing the upgrade,
as it's almost guaranteed that the slots won't have sent everything when the
source server is up and running.

Maybe simply check that all logical slots are currently active when running the
live check, so at least there's a good chance that they will still be at
shutdown, and will therefore send all the data to the subscribers? Having a
regression tests for that scenario would also be a good idea. Having an
uncommitted write transaction should be enough to cover it.