Hannu Krosing <hannu@tm.ee> writes:
> But if we would allow the scans to find the same keys twice without ill
> effects (as was suggested earlier, for using btrees to index arrays),
How is returning the same data twice not an "ill effect"?
> then we could possibly 1) copy the key to the right 2) wait for all
> right-to-left scans that have fallen between old and new values to pass
> and only then 3) delete the "old left" key.
How will you wait for scans that you know nothing of to go past?
Especially when they are going to be blocked by your own write lock
on the left page?
regards, tom lane