Robert Haas <robertmhaas@gmail.com> writes:
> I'm not quite sure how we'd decide whether to do a "really lazy"
> vacuum or the kind we do now. The case where this approach wins big
> is when there are few or no dead tuples. In that case, we do a lot of
> work looking at the indexes and we don't get much out of it; plus we
> scan the heap twice instead of just once.
Um, if there are *no* dead tuples then we don't look at the indexes
anyway, except for the vacuum-cleanup pass which I don't think you get
to decide you don't need. (You certainly don't get to decide that
unilaterally without the index AM's cooperation.) I'm less than
convinced that there's much gold to be mined here.
regards, tom lane