Re: BUG #15346: Replica fails to start after the crash

Greetings,

* Andres Freund (andres@anarazel.de) wrote:
> On August 28, 2018 11:44:09 AM GMT+09:00, Michael Paquier <michael@paquier.xyz> wrote:
> >On Sat, Aug 25, 2018 at 09:54:39AM +0200, Alexander Kukushkin wrote:
> >> Why the number of tuples in the xlog is greater than the number of
> >> tuples on the index page?
> >> Because this page was already overwritten and its LSN is HIGHER than
> >> the current LSN!
> >
> >That's annoying.  Because that means that the control file of your
> >server maps to a consistent point which is older than some of the
> >relation pages.  How was the base backup of this node created?  Please
> >remember that when taking a base backup from a standby, you should
> >backup the control file last, as there is no control of end backup with
> >records available.  So it seems to me that the origin of your problem
> >comes from an incorrect base backup expectation?
>
> Uh, where is that "control file last" bit coming from?

pg_basebackup copies it last.  The comments should probably be improved
as to *why* but my recollection is that it's, at least in part, to
ensure the new cluster can't be used until it's actually a complete
backup.

Thanks!

Stephen