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

On Thu, Aug 10, 2023 at 10:37:04PM +0900, Masahiko Sawada wrote:
> On Thu, Aug 10, 2023 at 12:52 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > Are you suggesting doing this before we start the old cluster or after
> > we stop the old cluster? I was thinking about the pros and cons of
> > doing this check when the server is 'on' (along with other upgrade
> > checks something like the patch is doing now) versus when the server
> > is 'off'. I think the advantage of doing it when the server is 'off'
> > (after check_and_dump_old_cluster()) is that it will be ensured that
> > there is no extra WAL that could be generated during the upgrade and
> > has not been verified against confirmed_flush_lsn location. But OTOH,
> > to retrieve slot information when the server is 'off', we need a
> > separate utility or probably a functionality for the same in
> > pg_upgrade and also some WAL reading stuff which sounds to me like a
> > larger change that may not be warranted here. I think anyway the extra
> > WAL (if any got generated during the upgrade) won't be required after
> > the upgrade so not convinced to make such a check while the server is
> > 'off'. Are there reasons which make it better to do this while the old
> > cluster is 'off'?
>
> What I imagined is that we do this check before
> check_and_dump_old_cluster() while the server is 'off'. Reading the
> slot state file would be simple and I guess we would not need a tool
> or cli program for that.

Agreed.

> BTW this check would not be able to support live-check but I think
> it's not a problem as this check with a running server will never be
> able to pass.

Agreed.

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Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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