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

On Thu, 2008-11-20 at 22:41 +0900, Fujii Masao wrote:

> 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 It continues waiting for the XLOG file with out-of-date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.

We've discussed this before. My answer is the same: you are assuming it
is safe to re-enter recovery, which is not correct (currently). You are
also assuming that taking a base backup is an expensive operation - it
need not be so if you simply move only the files/data that have changed,
e.g. rsync.

So if you want this to work, hacking pg_standby is not the way to do it.
But I'm not convinced there is a problem worth solving.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support