Re: Use pg_rewind when target timeline was switched

On Mon, Jul 20, 2015 at 9:18 PM, Alexander Korotkov
<a.korotkov@postgrespro.ru> wrote:
> attached patch allows pg_rewind to work when target timeline was switched.
> Actually, this patch fixes TODO from pg_rewind comments.
>
>   /*
>    * Trace the history backwards, until we hit the target timeline.
>    *
>    * TODO: This assumes that there are no timeline switches on the target
>    * cluster after the fork.
>    */
>
> This patch allows pg_rewind to handle data directory synchronization is much
> more general way. For instance, user can return promoted standby to old
> master.

Yes. That would be useful.

> In this patch target timeline history is exposed as global variable. Index
> in target timeline history is used in function interfaces instead of
> specifying TLI directly. Thus, SimpleXLogPageRead() can easily start reading
> XLOGs from next timeline when current timeline ends.

The implementation looks rather neat by having a first look at it, but
the attached patch fails to compile:
pg_rewind.c:488:4: error: use of undeclared identifier 'targetEntry'
                        targetEntry = &targetHistory[i];
                        ^
Nice to see as well that this has been added to the CF of September.