■ダイクストラ計算を使った方法(一般的なやりかた)
tomioka_db_b=# SELECT seq, node, edge, b.cost FROM pgr_dijkstra('SELECT gid as id, source, target, cost, reverse_cost FROM ways',1, 11) a INNER JOIN ways b ON (a.edge = b.gid) ORDER BY seq;
seq | node | edge | cost
-----+------+------+------------------------
1 | 1 | 2 | 8.518550262944416e-06
2 | 2 | 3 | 9.420518456308501e-05
3 | 3 | 4 | 2.6662995399998606e-05
4 | 4 | 6 | 2.1389117484400878e-05
5 | 5 | 7 | 4.6563628817813256e-06
6 | 6 | 8 | 1.3184236987589488e-05
7 | 7 | 9 | 6.438782425766514e-06
8 | 8 | 10 | 3.92599380897713e-05
9 | 9 | 11 | 3.1320245670872654e-05
10 | 10 | 12 | 1.7193010226696205e-05
■ところが、こうすると、2番目の最短距離が算出できます。
tomioka_db_b=# SELECT seq, node, edge, b.cost FROM pgr_ksp('SELECT gid as id, source, target, cost, reverse_cost FROM ways',1, 11, 2) a INNER JOIN ways b ON (a.edge = b.gid) ORDER BY seq;
seq | node | edge | cost
-----+------+------+------------------------
1 | 1 | 2 | 8.518550262944416e-06
2 | 2 | 3 | 9.420518456308501e-05
3 | 3 | 4 | 2.6662995399998606e-05
4 | 4 | 6 | 2.1389117484400878e-05
5 | 5 | 7 | 4.6563628817813256e-06
6 | 6 | 8 | 1.3184236987589488e-05
7 | 7 | 9 | 6.438782425766514e-06
8 | 8 | 10 | 3.92599380897713e-05
9 | 9 | 11 | 3.1320245670872654e-05
10 | 10 | 12 | 1.7193010226696205e-05
12 | 1 | 2 | 8.518550262944416e-06
13 | 2 | 1214 | 7.368115779153013e-06
14 | 792 | 118 | 8.976775615866592e-06
15 | 95 | 119 | 9.423341104506603e-05
16 | 96 | 121 | 2.578196166482512e-05
17 | 97 | 123 | 2.35136729002621e-05
18 | 98 | 125 | 6.587696385101331e-06
19 | 99 | 126 | 1.0007051975223507e-05
20 | 863 | 1313 | 7.188606587820858e-06
21 | 6 | 8 | 1.3184236987589488e-05
22 | 7 | 9 | 6.438782425766514e-06
23 | 8 | 10 | 3.92599380897713e-05
24 | 9 | 11 | 3.1320245670872654e-05
25 | 10 | 12 | 1.7193010226696205e-05
10番目までを出したかったら、上記の"2"を、"10"にすれば出てきます。
綺麗に直す方法については、がんばって下さい。