Actually, I guess it's the pid 47457 (COPY process) who is actually running the xid 73322726. In that case that's the same thing Masahiko Sawada reported [1].
Related, but not the same. It would be nice if they didn't block, but if they do have to block, shouldn't it wait on a semaphore, rather than doing a tight loop? It looks like maybe a latch didn't get reset when it should have or something.
