Re: Hot standby, recovery infra

On Thu, 2009-02-05 at 09:28 +0200, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> >> We could avoid that by performing a good old startup checkpoint, but I 
> >> quite like the fast failover time we get without it.
> > 
> > ISTM it's either slow failover or (fast failover, but restart archive
> > recovery if crashes).
> > 
> > I would suggest that at end of recovery we write the last LSN to the
> > control file, so if we crash recover then we will always end archive
> > recovery at the same place again should we re-enter it. So we would have
> > a recovery_target_lsn that overrides recovery_target_xid etc..
> 
> Hmm, we don't actually want to end recovery at the same point again: if 
> there's some updates right after the database came up, but before the 
> first checkpoint and crash, those actions need to be replayed too.

I think we do need to. Crash recovery is supposed to return us to the
same state. Where we ended ArchiveRecovery is part of that state. 

It isn't for crash recovery to decide that it saw a few more
transactions and decided to apply them anyway. The user may have
specifically ended recovery to avoid those additional changes from
taking place.

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