On Tue, 2013-05-28 at 19:51 -0400, Robert Haas wrote:
> > If we just wanted to reduce read cost, why not just take a simpler
> > approach and give the visibility map a "isfrozen" bit? Then we'd know
> > which pages didn't need rescanning without nearly as much complexity.
>
> That would break pg_upgrade, which would have to remove visibility map
> forks when upgrading. More importantly, it would require another
> round of complex changes to the write-ahead logging in this area.
> It's not obvious to me that we'd end up ahead of where we are today,
> although perhaps I am a pessimist.
If we removed PD_ALL_VISIBLE, then this would be very simple, right? We
would just follow normal logging rules for setting the visible or frozen
bit.
Regards,Jeff Davis