Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> A much more common ocurrence is tuple locks. We block in an Xid in that
> case; and this has been a frequent question in the mailing lists and
> IRC.
> I think it would be very nice to be able to report something to the
> user; however, I'm not seeing the mechanism.
At least for tuple locks, the information is already visible, because we
have a "real" lock on the target tuple before we try to lock the current
holder's VXID. So I think this isn't so much a question of needing more
low-level mechanism as one of providing a more useful view --- some kind
of self-join on pg_locks is needed.
regards, tom lane