session-1:
vac=> begin;
BEGIN
vac=> lock table t in row share mode;
LOCK TABLE
session-2:
vac=> begin;
BEGIN
vac=> lock table t in row share mode;
LOCK TABLE
session-3:
vac=> begin;
BEGIN
vac=> lock table t in row exclusive mode;
LOCK TABLE
session-1:
vac=> lock table t in share row exclusive mode;
--waiting (conflicts with session-3 lock)
session-2:
vac=> lock table t in share row exclusive mode;
NOTICE: Deadlock detected -- See the lock(l) manual page for a possible cause.
ERROR: WaitOnLock: error on wakeup - Aborting this transaction
???
ShareLockExclusive mode doesn't conflict with RowShare mode
(though it is self-conflicting mode).
Comments in DeadLockCheck() say: /* * For findlock's wait queue, we are interested in * procs who are
blockedwaiting for a write-lock on * the table we are waiting on, and already hold a * lock on it. We first
checkto see if there is an * escalation deadlock, where we hold a readlock and * want a writelock, and someone
elseholds readlock * on the same table, and wants a writelock. * * Basically, the test is, "Do we both hold
somelock on * findlock, and we are both waiting in the lock * queue?" bjm */
Unfortunately, this is not right test any more -:(.
Vadim
