Understanding of LOCK and pg_sleep interaction

Hi,

In trying to setup a test for a LOCK 'table' algorithm I attempt to execute
two transactions where the first one issues a pg_sleep(10) while 'table' is
locked and the second one attempts LOCK 'table' during the time when the
pg_sleep is executing. When pg_sleep() returns in the first transaction the
subsequent statement is not executed. Meanwhile, the second transaction
continues to wait for the lock. Thus, a deadlock has occurred. I am doing
my testing within PostGreSQL Maestro running as a "script" and issuing BEGIN
and COMMIT statements around the desired transaction commands.

I would expect the first transaction to finish following the 10 second sleep
at which point the first transaction would be able to start.

PostgreSQL 9.0.3 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.4.real
(Ubuntu 4.4.3-4ubuntu5) 4.4.3, 64-bit

Either script run alone works just fine - it is just when run in tandem as
described is neither able to complete.

What am I doing/understanding incorrectly or is this undesirable behavior?

Thanks,

David J.

===============================

--Transaction 1

begin;

delete from locktest;

LOCK locktest;

INSERT INTO locktest (scope, value) VALUES ('TEST','1');

INSERT INTO locktest (scope, value) VALUES ('TEST','2');

select pg_sleep(10);

rollback; --or commit [This doesn't execute if I begin transaction 2]

>>pg_stat_activity

<IDLE> in transaction

==============================

--Transaction 2

begin;

LOCK locktest; --[This never completes if executed during pg_sleep(10)]

INSERT INTO locktest (scope, value) VALUES ('TEST','3');

commit;

>>pg_stat_activity

LOCK locktest

===============================

>>Attempt at pg_lock results; executed AFTER the 10 second pg_sleep
returned.

locktype database relation page
tuple virtualxid transactionid classid objid
objsubid virtualtransaction pid mode
granted

transactionid
101091 15/359 13752
ExclusiveLock True

relation 623943 853698
15/359 13752 RowExclusiveLock True

relation 623943 853698
15/359 13752 AccessExclusiveLock True

relation 623943 10985
18/153 13770 AccessShareLock True

relation 623943 853696
15/359 13752 AccessShareLock True

virtualxid
18/153
18/153 13770 ExclusiveLock True

virtualxid
15/359
15/359 13752 ExclusiveLock True

relation 623943 853702
15/359 13752 RowExclusiveLock True

virtualxid
17/438
17/438 13754 ExclusiveLock True

relation 623943 853698
17/438 13754 AccessExclusiveLock False