pgr_ksp (V 2.0) - K-Shortest Path

Name

pgr_ksp — Returns the “K” shortest paths.

Synopsis

The K shortest path routing algorithm based on Yen’s algorithm. “K” is the number of shortest paths desired. Returns a set of pgr_costResult3 (seq, id1, id2, id3, cost) rows, that make up a path.

pgr_costResult3[] pgr_ksp(sql text, source integer, target integer,
                         paths integer, has_rcost boolean);

Warning

This signature is being deprecated in version 2.1, Please use it without the has_rcost flag instead.

  • for undirected graph. pgr_ksp(sql, source, target, distance, directed:=false)
  • for directed graph. pgr_ksp(sql, source, target, distance, directed:=true)

See pgr_ksp - K-Shortest Path

Description

sql:

a SQL query, which should return a set of rows with the following columns:

SELECT id, source, target, cost, [,reverse_cost] FROM edge_table
id:int4 identifier of the edge
source:int4 identifier of the source vertex
target:int4 identifier of the target vertex
cost:float8 value, of the edge traversal cost. A negative cost will prevent the edge from being inserted in the graph.
reverse_cost:(optional) the cost for the reverse traversal of the edge. This is only used when has_rcost the parameter is true (see the above remark about negative costs).
source:

int4 id of the start point
target:

int4 id of the end point
paths:

int4 number of alternative routes
has_rcost:

if true, the reverse_cost column of the SQL generated set of rows will be used for the cost of the traversal of the edge in the opposite direction.

Returns set of pgr_costResult[]:

seq:sequence for ording the results
id1:route ID
id2:node ID
id3:edge ID (0 for the last row)
cost:cost to traverse from id2 using id3

KSP code base taken from http://code.google.com/p/k-shortest-paths/source.

History

  • New in version 2.0.0

Examples

  • Without reverse_cost
 SELECT seq, id1 AS route, id2 AS node, id3 AS edge, cost
  FROM pgr_ksp(
    'SELECT id, source, target, cost FROM edge_table',
    7, 12, 2, false
  );
 seq | route | node | edge | cost
-----+-------+------+------+------
   0 |     0 |    7 |    6 |    1
   1 |     0 |    8 |    7 |    1
   2 |     0 |    5 |    8 |    1
   3 |     0 |    6 |    9 |    1
   4 |     0 |    9 |   15 |    1
   5 |     0 |   12 |   -1 |    0
   6 |     1 |    7 |    6 |    1
   7 |     1 |    8 |    7 |    1
   8 |     1 |    5 |    8 |    1
   9 |     1 |    6 |   11 |    1
  10 |     1 |   11 |   13 |    1
  11 |     1 |   12 |   -1 |    0
(12 rows)
  • With reverse_cost
 SELECT seq, id1 AS route, id2 AS node, id3 AS edge, cost
  FROM pgr_ksp(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    7, 12, 2, true
  );
 seq | route | node | edge | cost
-----+-------+------+------+------
   0 |     0 |    7 |    6 |    1
   1 |     0 |    8 |    7 |    1
   2 |     0 |    5 |    8 |    1
   3 |     0 |    6 |    9 |    1
   4 |     0 |    9 |   15 |    1
   5 |     0 |   12 |   -1 |    0
   6 |     1 |    7 |    6 |    1
   7 |     1 |    8 |    7 |    1
   8 |     1 |    5 |    8 |    1
   9 |     1 |    6 |   11 |    1
  10 |     1 |   11 |   13 |    1
  11 |     1 |   12 |   -1 |    0
(12 rows)

The queries use the Sample Data network.