On Thu, May 30, 2013 at 1:39 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, May 30, 2013 at 9:33 AM, Heikki Linnakangas > <hlinnakan...@vmware.com> wrote: >> The reason we have to freeze is that otherwise our 32-bit XIDs wrap around >> and become ambiguous. The obvious solution is to extend XIDs to 64 bits, but >> that would waste a lot space. The trick is to add a field to the page header >> indicating the 'epoch' of the XID, while keeping the XIDs in tuple header >> 32-bit wide (*). > > (3) You still need to periodically scan the entire relation, or else > have a freeze map as Simon and Josh suggested.
Why is this scan required? Also, what happens if you delete a tuple on a page when another tuple on the same page with age > 2^32 that is still in an open transaction? merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
