SQL - PostgreSQL - find locked transactions

SELECT bl.pid AS blocked_pid, a.usename AS blocked_user,
        ka.current_query AS blocking_statement, now() - ka.query_start AS blocking_duration,
        kl.pid AS blocking_pid, ka.usename AS blocking_user, a.current_query AS blocked_statement,
        now() - a.query_start AS blocked_duration
 FROM pg_catalog.pg_locks bl
      JOIN pg_catalog.pg_stat_activity a
      ON bl.pid = a.procpid
      JOIN pg_catalog.pg_locks kl
           JOIN pg_catalog.pg_stat_activity ka
           ON kl.pid = ka.procpid
      ON bl.transactionid = kl.transactionid AND bl.pid != kl.pid
 WHERE NOT bl.GRANTED;