Re: How should pg_standby get over the gap of timeline?

Fujii Masao wrote:
> Hi, Heikki. Thanks for the comment!
>
> On Thu, Nov 20, 2008 at 11:24 PM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> Fujii Masao wrote:
>>> In the current Synch Rep patch, the standby cannot catch up with the
>>> primary which has a bigger timeline.
>> That would only happen if you've performed an archive recovery in the
>> primary. If you've done PITR in the primary, I don't think there's any
>> guarantee that it's even possible to catch up the standby. The standby might
>> already have replayed a WAL file from an earlier timeline, that isn't part
>> of the history of the bigger timeline.
>
> I assume the situation of making the standby (the original primary) catch up
> with the primary (the original standby) after failover. Since a timeline is
> incremented when a failover finishes archive recovery on a standby, the
> timelines differ between two servers.

That seems like a dangerous assumption. What if the standby had fallen
behind before the failover? It's not safe to failover back to the
original primary in that case. We'd need some kind of safeguards against
that.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com