Re: pg_upgrade resets timeline to 1

Re: Noah Misch 2015-05-28 <20150528072721(dot)GA4102649(at)tornado(dot)leadboat(dot)com>
> > I've just had trouble getting barman to work again after a 9.1->9.4.2
> > upgrade, and I think part of the problem was that the WAL for this
> > cluster got reset from timeline 2 to 1, which made barman's incoming
> > WALs processor drop the files, probably because the new filename
> > 0001... is now "less" than the 0002... before.
>
> It looks like an upgrade from 9.1.x to 9.3.0 or later has always set the new
> timeline identifier (TLI) to 1. My testing confirms this for an upgrade from
> 9.1.16 to 9.4.1 and for an upgrade from 9.1.16 to 9.4.2, so I failed to
> reproduce your report. Would you verify the versions you used? If you were
> upgrading from 9.3.x, I _can_ reproduce that.

Sorry, the "9.1" was a typo, the system was on 9.2.11 before/during
pg_upgrade.

> Do note this in the documentation, though:
>
> The archive command should generally be designed to refuse to overwrite any
> pre-existing archive file. This is an important safety feature to preserve
> the integrity of your archive in case of administrator error (such as
> sending the output of two different servers to the same archive directory).
> -- http://www.postgresql.org/docs/devel/static/continuous-archiving.html

(Except that this wasn't possible in practise since ~9.2 until very
recently because some files got archived again during a timeline
switch :-/ )

Christoph
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