> What's the verdict on relaxing the "live tuple's ctid doesn't
> change rule"? If we did allow that within a page, what would
> we need to change?
I already said this, but why would this need to be visible from the
outside ?
A few assumptions:no back pointersindexes only point at slots marked as roots (and non hot tuples)
During vacuum, you swap the tuples and keep a stub at the slot that the
user's ctid might be pointing at. You mark the stub to detect this
situation.
When a select/update by ctid comes along it needs to do one step to the
root
and use that tuple instead.
It needs a second vacuum (or a per page vacuum during update) to remove
the
extra stub when it is dead and not recently dead.
I fail to see the hole.
Andreas