Find Locks
From PostgreSQL wiki
SELECT l1.*, l2.virtualtransaction, l2.pid, l2.mode, l2.granted FROM pg_locks l1 JOIN pg_locks l2 ON ( ( l1.locktype, l1.DATABASE, l1.relation, l1.page, l1.tuple, l1.virtualxid, l1.transactionid, l1.classid, l1.objid, l1.objsubid ) IS NOT DISTINCT FROM ( l2.locktype, l2.DATABASE, l2.relation, l2.page, l2.tuple, l2.virtualxid, l2.transactionid, l2.classid, l2.objid, l2.objsubid ) ) WHERE NOT l1.granted AND l2.granted;