Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Sorry, I missed that.
And you evidently still didn't understand it. Locking both pages does
not fix the problem, because it doesn't guarantee that there's not a
concurrent indexscan in flight from one to the other. If you move items
from one page to the other in the opposite direction from the way the
scan is going, then it will miss those items. If we try to fix this by
making scans lock one page before releasing the previous, then we'll
create a bunch of deadlock cases.
regards, tom lane