On Wed, 2010-02-24 at 10:40 +0200, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> > I would add that both Heikki and Greg Stark have argued at length that
> > the visibility map cannot be relied upon in production systems.
>
> It cannot be relied on *in its current form*. There's a hole in crash
> recovery where it can be left in an inconsistent state. That obviously
> needs to be fixed before it is relied on for index-only-scans or similar
> purposes, but it's not an insurmountable problem.
I was referring to earlier discussions around the use of that
information for use in partitioning. At that time it was argued the
technique would be fragile and unusable in production systems, even
assuming the information was accurate. Regrettably, I agree: even a
light write workload is sufficient to render the technique useless and
designing systems that relied upon that would be risky.
-- Simon Riggs www.2ndQuadrant.com