Robert Haas <robertmhaas@gmail.com> writes:
> I think that the indexes only need to be scanned if the VACUUM finds
> dead tuples. But even 1 dead tuple will cause a complete scan of
> every index. I've complained about this before and I think there's
> room for improvement here, but nobody's been motivated enough to
> pursue this yet.
The thing that's been speculated about in the past is having some
threshold larger than 1 on the minimum number of dead tuples needed
to cause a cleanup pass. It wouldn't be hard to implement, if you
could get consensus on what the threshold should be. I'd think
some algorithm similar to the autovacuum thresholds might be
appropriate. It's not quite clear how this would interact with
HOT pruning, though.
regards, tom lane
