Re: Hot standby and b-tree killed items

On Sat, 2008-12-20 at 09:21 +0200, Heikki Linnakangas wrote:
> Gregory Stark wrote:
> > Simon Riggs <simon@2ndQuadrant.com> writes:
> > 
> >> Increasing the waiting time increases the failover time and thus
> >> decreases the value of the standby as an HA system. Others value high
> >> availability higher than you and so we had agreed to provide an option
> >> to allow the max waiting time to be set.
> > 
> > Sure, it's a nice option to have. But I think the default should be to pause
> > WAL replay.
> 
> I think I agree that pausing should be the default. If for no other 
> reason, because I can't think of a good default for max_standby_delay.

I would rather err on the side of caution. If we do as you suggest,
somebody will lose their database and start shouting "stupid default".
So I would suggest we set it to say 5 seconds to start with and let
people that read the manual set it higher, or at least read the manual
after they receive their first query cancellation.

> It would be nice to have a setting to specify the max. amount of 
> unapplied WAL before killing queries. 

Agreed.

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