keith@pgods=# select pg_try_advisory_lock(hashtext('summarize_hits_today'));
 pg_try_advisory_lock
----------------------
 f
(1 row)

Time: 1.005 ms
keith@pgods=# select pg_advisory_unlock(hashtext('summarize_hits_today'));
WARNING:  you don't own a lock of type ExclusiveLock
 pg_advisory_unlock
--------------------
 f
(1 row)

Time: 0.528 ms
keith@pgods=# select pg_try_advisory_lock(hashtext('summarize_hits_today'));
 pg_try_advisory_lock
----------------------
 f
(1 row)

Time: 0.578 ms