View locking transactions (PostgreSQL)

From ben.goodacre.name/tech

SELECT pg_class.relname, pg_locks.transactionid, pg_locks.mode, pg_locks.granted as "g",
substr(pg_stat_activity.current_query,1,30), pg_stat_activity.query_start,
age(now(),pg_stat_activity.query_start) as "age", pg_stat_activity.procpid
FROM pg_stat_activity,pg_locks
left outer join pg_class on
(pg_locks.relation = pg_class.oid)
WHERE pg_locks.pid=pg_stat_activity.procpid;