This algorithm is designed to return multiple alternative paths, so it not only finds the shortest path, but also K-1 alternative paths. pgRouting implementation is based on Jin J. Yen's works.

The basic usage is as follows:

select * from pgr_ksp('select gid as id, source, target, cost, x1, y1, x2, y2 from pgr.ways', 79240, 9064, 2); 

The output is very similar to what we have seen so far; the difference is the presence of an additional column that indicates the path identifier:

seq|path_id|path_seq| node| edge|             cost|         agg_cost
---+-------+--------+-----+-----+-----------------+-----------------
  1|      1|       1|79240|69362| 0.00152459527744|                0
  2|      1|       2|52082|44175|0.000969276126804|0.001524595277445
...

When we visualize the preceding output, it looks as follows: