Robert Haas wrote: > On Mon, Jul 27, 2015 at 2:32 PM, Alvaro Herrera > <alvhe...@2ndquadrant.com> wrote:
> > I think this is already possible, is it not? You just have to look for > > an identically-identified pg_locks entry with granted=true. That gives > > you a PID and vxid/xid. You can self-join pg_locks with that, and join > > to pg_stat_activity. > > > > I remember we discussed having a layer of system views on top of > > pg_stat_activity and pg_locks, probably defined recursively, that would > > show the full graph of waiters/lockers. > > It isn't necessarily the case that A is waiting for a unique process > B. It could well be the case that A wants AccessExclusiveLock and > many processes hold a variety of other lock types. Sure, but I don't think this makes it impossible to figure out who's locking who. I think the only thing you need other than the data in pg_locks is the conflicts table, which is well documented. Oh, hmm, one thing missing is the ordering of the wait queue for each locked object. If process A holds RowExclusive on some object, process B wants ShareLock (stalled waiting) and process C wants AccessExclusive (also stalled waiting), who of B and C is woken up first after A releases the lock depends on order of arrival. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
