pgsql-bugs(at)postgresql(dot)org writes:
> the ?# (geometric intersection) operator for paths iterates over point
> pairs in each path testing for intersection. however, it ignores the
> last->first point pair for closed paths.
Looks like a bug to me too; and path_distance, path_length, dist_ppath
also fail to consider the closing segment of a closed path.
Fixed for 7.2.
regards, tom lane