On Fri, 2012-11-16 at 16:09 +0100, Andres Freund wrote:
> As far as I understand the code the crash-safety aspects of the
> visibilitymap currently rely on on having the knowledge that ALL_VISIBLE
> has been cleared during a heap_(insert|update|delete). That allows
> management of the visibilitymap without it being xlogged itself which
> seems pretty important to me.
It looks like the xlrec does contain a "cleared all visible" flag in it,
and it uses that to clear the VM as well as PD_ALL_VISIBLE.
So, it still seems achievable, and maybe not even a large patch, to do
away with PD_ALL_VISIBLE without a lot of performance risk.
Regards,Jeff Davis