PostgreSQL Lock Chain: Who Is Blocking Whom?

SELECT blocked.pid                AS blocked_pid,
       blocked.usename            AS blocked_user,
       left(blocked.query, 120)   AS blocked_query,
       blocker.pid                AS blocking_pid,
       blocker.usename            AS blocking_user,
       blocker.state              AS blocking_state,
       left(blocker.query, 120)   AS blocking_query,
       now() - blocked.query_start AS waiting_for
FROM pg_stat_activity blocked
JOIN LATERAL unnest(pg_blocking_pids(blocked.pid)) AS b(pid) ON true
JOIN pg_stat_activity blocker ON blocker.pid = b.pid
ORDER BY waiting_for DESC;