Re: Hot standby, recovery infra

On Thu, 2009-02-05 at 10:31 +0200, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> > On Thu, 2009-02-05 at 09:28 +0200, Heikki Linnakangas wrote:
> > 
> >>>> I've changed the way minRecoveryPoint is updated now anyway, so it no 
> >>>> longer happens every XLogFileRead().
> >>> Care to elucidate?
> >> I got rid of minSafeStartPoint, advancing minRecoveryPoint instead. And 
> >> it's advanced in XLogFlush instead of XLogFileRead. I'll post an updated 
> >> patch soon.
> > 
> > Why do you think XLogFlush is called less frequently than XLogFileRead?
> 
> It's not, but we only need to update the control file when we're 
> "flushing" an LSN that's greater than current minRecoveryPoint. And when 
> we do update minRecoveryPoint, we can update it to the LSN of the last 
> record we've read from the archive.

So we might end up flushing more often *and* we will be doing it
potentially in the code path of other users.

This change seems speculative and also against what has previously been
agreed with Tom. If he chooses not to comment on your changes, that's up
to him, but I don't think you should remove things quietly that have
been put there through the community process, as if they caused
problems. I feel like I'm in the middle here. 

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