darkk select from order by time time node_id ------ --------- 10 10 ro

darkk=> select * from t order by time;
 time | node_id 
------+---------
    1 |       1
    2 |       1
    3 |       2
    4 |       2
    5 |       1
    6 |       1
    7 |       3
    8 |       1
    9 |       1
   10 |       1
(10 rows)

darkk=> 
SELECT 
    node_id, 
    time AS "from", 
    (SELECT 
        max(time) 
     FROM t as future 
     WHERE 
        future.time >= now.time 
        AND NOT EXISTS (
            SELECT 1 FROM t AS foo 
            WHERE foo.node_id != now.node_id AND foo.time BETWEEN now.time AND future.time) 
    ) AS "to" 
FROM t AS now 
WHERE NOT EXISTS ( 
    SELECT 1 FROM t AS past 
    WHERE past.node_id = now.node_id AND past.time = (SELECT max(time) FROM t AS foo WHERE foo.time < now.time ))
ORDER BY "from";
 node_id | from | to 
---------+------+----
       1 |    1 |  2
       2 |    3 |  4
       1 |    5 |  6
       3 |    7 |  7
       1 |    8 | 10
(5 rows)