Re: PITR promote bug: Checkpointer writes to older timeline

On Thu, Mar 04, 2021 at 10:28:31AM +0900, Kyotaro Horiguchi wrote:
> read_local_xlog_page() works as a part of logical decoding and has
> responsibility to update ThisTimeLineID properly.  As the comment in
> the function, it is the proper place to update ThisTimeLineID since we
> miss a timeline change if we check it earlier and the function uses
> the value just after. So we cannot change that behavior of the
> function.  That is, neither of them doesn't seem to be the right fix.
> 
> The confusion here is that there's two ThisTimeLineID's here. The
> previous TLI for read and the next TLI to write.  Most part of the
> function is needed to read a 2pc recrod so the ways we can take here
> is:
> 
> 1. Somehow tell the function not to update ThisTimeLineID in specific
>   cases. This can be done by xlogreader private data but this doesn't
>   seem reasonable.
> 
> 2. Restore ThisTimeLineID after calling XLogReadRecord() in the
>   *caller* side.  This is what came up to me first but I don't like
>   this, too, but I don't find better fix.  way.

I have not looked in details at the solutions proposed here, but could
it be possible to have a TAP test at least please?  Seeing the script
from the top of the thread, it should not be difficult to do so.  I
would put that in a file different than 009_twophase.pl, within
src/test/recovery/.
--
Michael