george young <gry@ll.mit.edu> writes:
> update steps set x=x||'X' from steps s where steps.key1=s.key1 and steps.key2=s.key2 and step.ctid<s.ctid;
> But this fails because there is no less-than operator (or function) on
> type "tid".
Probably a good thing, too, since if there was it wouldn't have anything
reliable to do with the age of the tuple.
regards, tom lane