On 15 December 2012 12:42, Pavan Deolasee <pavan.deolasee@gmail.com> wrote:
> We discussed this idea in the past [1] and Robert recently again
> mentioned this in another thread [2]. Please see a rebased/revised
> patch attached with the mail. This is mostly similar to what I's
> submitted in [1] except some additions to also compute visibility
> cut-off XID. I also removed a warning that I'd added to the previous
> patch to report the case when the page's all-visible bit is already
> set, but our HOT prune scan finds it otherwise. This is not to hide
> the warning the earlier reviewer had reported, but I think its not
> required because we do those consistency checks at other places
> anyways.
Doing that only makes sense when we're running a SELECT. Setting the
all visible bit immediately prior to an UPDATE that clears it again is
pointless effort, generating extra work for no reason.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services