Re: [HACKERS] tablelevel and rowlevel locks

Alvaro Herrera Munoz <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> Anyway, I think the LOCK structure represents something that can be locked.

Right.

> The PROCLOCK struct represents that some process is holding a lock on said
> object.

IIRC, a PROCLOCK is created as soon as some backend tries to lock some
lockable object. So the PROCLOCK may only indicate that that backend is
waiting for a lock on that object, not that it already has one.

> That may be the reason why you are seeing that a lock is held by more
> than one process at the same time (while in fact some of them are probably
> _waiting_ for the lock).

Also keep in mind that we use a lot of sharable lock modes --- so it's
entirely likely that multiple processes actually do have locks on the
same object. That's not wrong if their lock modes don't conflict.

regards, tom lane