How should pg_standby get over the gap of timeline?

Hi,

In the current Synch Rep patch, the standby cannot catch up with the
primary which has a bigger timeline. So, whenever making the standby
catch up, a fresh base backup is required. This is obviously undesirable,
and I'd like to get rid of this restriction.

Postgres itself can recover up to a bigger timeline without a base
backup. The remaining problem is that pg_standby cannot get over the
gap of timeline. It continues waiting for the XLOG file with out-of-date
timeline, and redo doesn't progress.

My idea is that introducing a new option into pg_standby, which makes
the restoring fail if there is the XLOG file with the same logid and segid
even if the target file doesn't exist. Once failing to restore, the startup
process can switch the timeline and try to restore the XLOG file with
new timeline.

Is this idea reasonable? Any comments welcome!

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center