Użyj rekurencyjnego cte z array[array[source, destination]] jako kolumna agregacji:
with recursive cte(source, destination, path) as (
select source, destination, array[array[source, destination]]
from points
union all
select p.source, p.destination, path || array[p.source, p.destination]
from cte c
join points p on c.destination = p.source
where not array[array[p.source, p.destination]] <@ path
)
select distinct on (path[1:1]) path
from (
select distinct on (source, destination) *
from cte
order by source, destination, array_length(path, 1) desc
) s
order by path[1:1], array_length(path, 1) desc;
path
---------------------
{{1,2},{2,3},{3,7}}
{{5,7}}
{{9,12}}
(3 rows)
