"Heikki Linnakangas" <heikki@enterprisedb.com> writes:
> Tom argued that following the tuple chain is cheap enough, and might
> even be cheaper than what we have now, that we don't need to prune just
> for the purpose of keeping the chains short. To which I pointed out that
> currently, without HOT, we mark index tuples pointing to dead tuples as
> killed to avoid following them in the future, so HOT without pruning is
> not cheaper than what we have now.
That hack only works in plain indexscans, though, not bitmapped scans.
Anyway, I remain unconvinced that the chains would normally get very
long in the first place, if we could prune when updating.
The we-already-pinned-the-page problem is a bit nasty but may not be
insurmountable.
regards, tom lane