SELECT A.rid As a_rid, B.rid As b_rid, A.rast &< B.rast As overleft
FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;
a_rid | b_rid | overleft
------+-------+----------
2 | 2 | t
2 | 3 | f
2 | 1 | f
3 | 2 | t
3 | 3 | t
3 | 1 | f
1 | 2 | t
1 | 3 | t
1 | 1 | t
