On Sat, Jan 14, 2012 at 5:42 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> Other than that, it seems like we might be converging on a workable
> solution: if hot_standby_feedback=off, disable index-only scans for
> snapshots taken during recovery; if hot_standby_feedback=on, generate
> recovery conflicts when a snapshot's xmin precedes the youngest xmin
> on a page marked all-visible, but allow the use of index-only scans,
> and allow sequential scans to trust PD_ALL_VISIBLE. Off the top of my
> head, I don't see a hole in that logic...
Please use the logic described earlier. Using the existing mechanisms
and infrastructure is all we need here.
We want latestRemovedXid, not a new version of it via xmins. Keep
index-only scans enabled all the time and let conflicts be generated.
There are already mechanisms in place to handle conflicts, so avoiding
them another way is not required or desired.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
