"Florian G. Pflug" <fgp@phlo.org> writes:
> I can see how the EPQ machinery can be used to chain forward to the
> correct row to be updated, even if I originally found an older version
> (e.g. by searching for a specific ctid). But for non-"for
> update"-cursors, the newest version of the row returned by fetch could
> be modified such that it would have never been returned by fetch in the
> first place.
Yah, EPQ checks for that ... none of the situations you've mentioned are
any different from the case of an ordinary UPDATE that finds a row
that's been modified since its snapshot was taken. A cursor would just
make the time window a bit larger.
regards, tom lane