Re: Clarification in pg10's pgupgrade.html step 10 (upgrading standby servers)

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Michael Banck <michael(dot)banck(at)credativ(dot)de>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Andreas Joseph Krogh <andreas(at)visena(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Clarification in pg10's pgupgrade.html step 10 (upgrading standby servers)
Date: 2017-09-14 19:14:56
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On Wed, Sep 13, 2017 at 07:39:31PM +0200, Michael Banck wrote:
> On Tue, Sep 12, 2017 at 07:38:40PM -0400, Stephen Frost wrote:
> > Further, really, I think we should provide a utility to do all of the
> > above instead of using rsync- and that utility should do some additional
> > things, such as:
> >
> > - Check that the control file on the primary and replica show that they
> > reached the same point prior to the pg_upgrade. If they didn't, then
> > things could go badly as there's unplayed WAL that the primary got
> > through and the replica didn't.
> >
> > - Not copy over unlogged data, or any other information that shouldn't
> > be copied across.
> >
> > - Allow the directory structures to be more different between the
> > primary and the replica than rsync allows (wouldn't have to have a
> > common subdirectory on the replica).
> >
> > - Perhaps other validation checks or similar.
> >
> > Unfortunately, this is a bit annoying as it necessairly involves running
> > things on both the primary and the replica from the same tool, without
> > access to PG, meaning we'd have to work through something else (such as
> > SSH, like rsync does, but then what would we do for Windows...?).
> Maybe pg_rewind's mechanism could be partially reused for this as it
> seems to accomplish something vaguely similar AIUI?

pg_rewind works at the WAL level while this is at the file system level.

Bruce Momjian <bruce(at)momjian(dot)us>

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