pgr_withPointsKSP - Proposed

pgr_withPointsKSP - Find the K shortest paths using Yen’s algorithm.

Warning

Proposed functions for next mayor release.

  • They are not officially in the current release.

  • They will likely officially be part of the next mayor release:

    • The functions make use of ANY-INTEGER and ANY-NUMERICAL

    • Name might not change. (But still can)

    • Signature might not change. (But still can)

    • Functionality might not change. (But still can)

    • pgTap tests have being done. But might need more.

    • Documentation might need refinement.

_images/boost-inside.jpeg

Boost Graph Inside

Availability

  • Version 2.2.0

    • New proposed function

Support

Description

Modifies the graph to include the points defined in the points_sql and using Yen algorithm, finds the \(K\) shortest paths.

Signatures

Summary

pgr_withPointsKSP(edges_sql, points_sql, start_pid, end_pid, K [, directed] [, heap_paths] [, driving_side] [, details])
RETURNS SET OF (seq, path_id, path_seq, node, edge, cost, agg_cost)

Using defaults

pgr_withPointsKSP(edges_sql, points_sql, start_pid, end_pid, K)
RETURNS SET OF (seq, path_id, path_seq, node, edge, cost, agg_cost)
Example

From point \(1\) to point \(2\) in \(2\) cycles

  • For a directed graph.

  • The driving side is set as b both. So arriving/departing to/from the point(s) can be in any direction.

  • No details are given about distance of other points of the query.

  • No heap paths are returned.

SELECT * FROM pgr_withPointsKSP(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, -2, 2);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |   -1 |    1 |  0.6 |        0
   2 |       1 |        2 |    2 |    4 |    1 |      0.6
   3 |       1 |        3 |    5 |    8 |    1 |      1.6
   4 |       1 |        4 |    6 |    9 |    1 |      2.6
   5 |       1 |        5 |    9 |   15 |  0.4 |      3.6
   6 |       1 |        6 |   -2 |   -1 |    0 |        4
   7 |       2 |        1 |   -1 |    1 |  0.6 |        0
   8 |       2 |        2 |    2 |    4 |    1 |      0.6
   9 |       2 |        3 |    5 |    8 |    1 |      1.6
  10 |       2 |        4 |    6 |   11 |    1 |      2.6
  11 |       2 |        5 |   11 |   13 |    1 |      3.6
  12 |       2 |        6 |   12 |   15 |  0.6 |      4.6
  13 |       2 |        7 |   -2 |   -1 |    0 |      5.2
(13 rows)

Complete Signature

Finds the \(K\) shortest paths depending on the optional parameters setup.

pgr_withPointsKSP(edges_sql, points_sql, start_pid, end_pid, K [, directed] [, heap_paths] [, driving_side] [, details])
RETURNS SET OF (seq, path_id, path_seq, node, edge, cost, agg_cost)
Example

From point \(1\) to vertex \(6\) in \(2\) cycles with details.

SELECT * FROM pgr_withPointsKSP(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, 6, 2, details := true);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |   -1 |    1 |  0.6 |        0
   2 |       1 |        2 |    2 |    4 |  0.7 |      0.6
   3 |       1 |        3 |   -6 |    4 |  0.3 |      1.3
   4 |       1 |        4 |    5 |    8 |    1 |      1.6
   5 |       1 |        5 |    6 |   -1 |    0 |      2.6
   6 |       2 |        1 |   -1 |    1 |  0.6 |        0
   7 |       2 |        2 |    2 |    4 |  0.7 |      0.6
   8 |       2 |        3 |   -6 |    4 |  0.3 |      1.3
   9 |       2 |        4 |    5 |   10 |    1 |      1.6
  10 |       2 |        5 |   10 |   12 |  0.6 |      2.6
  11 |       2 |        6 |   -3 |   12 |  0.4 |      3.2
  12 |       2 |        7 |   11 |   13 |    1 |      3.6
  13 |       2 |        8 |   12 |   15 |  0.6 |      4.6
  14 |       2 |        9 |   -2 |   15 |  0.4 |      5.2
  15 |       2 |       10 |    9 |    9 |    1 |      5.6
  16 |       2 |       11 |    6 |   -1 |    0 |      6.6
(16 rows)

Parameters

Parameter

Type

Description

edges_sql

TEXT

Edges SQL query as described above.

points_sql

TEXT

Points SQL query as described above.

start_pid

ANY-INTEGER

Starting point id.

end_pid

ANY-INTEGER

Ending point id.

K

INTEGER

Number of shortest paths.

directed

BOOLEAN

(optional). When false the graph is considered as Undirected. Default is true which considers the graph as Directed.

heap_paths

BOOLEAN

(optional). When true the paths calculated to get the shortests paths will be returned also. Default is false only the K shortest paths are returned.

driving_side

CHAR

(optional) Value in [‘b’, ‘r’, ‘l’, NULL] indicating if the driving side is:
  • In the right or left or

  • If it doesn’t matter with ‘b’ or NULL.

  • If column not present ‘b’ is considered.

details

BOOLEAN

(optional). When true the results will include the driving distance to the points with in the distance. Default is false which ignores other points of the points_sql.

Inner query

Column

Type

Default

Description

id

ANY-INTEGER

Identifier of the edge.

source

ANY-INTEGER

Identifier of the first end point vertex of the edge.

target

ANY-INTEGER

Identifier of the second end point vertex of the edge.

cost

ANY-NUMERICAL

Weight of the edge (source, target)

  • When negative: edge (source, target) does not exist, therefore it’s not part of the graph.

reverse_cost

ANY-NUMERICAL

-1

Weight of the edge (target, source),

  • When negative: edge (target, source) does not exist, therefore it’s not part of the graph.

Where:

ANY-INTEGER

SMALLINT, INTEGER, BIGINT

ANY-NUMERICAL

SMALLINT, INTEGER, BIGINT, REAL, FLOAT

Description of the Points SQL query

points_sql

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

Column

Type

Description

pid

ANY-INTEGER

(optional) Identifier of the point.

  • If column present, it can not be NULL.

  • If column not present, a sequential identifier will be given automatically.

edge_id

ANY-INTEGER

Identifier of the “closest” edge to the point.

fraction

ANY-NUMERICAL

Value in <0,1> that indicates the relative postition from the first end point of the edge.

side

CHAR

(optional) Value in [‘b’, ‘r’, ‘l’, NULL] indicating if the point is:

  • In the right, left of the edge or

  • If it doesn’t matter with ‘b’ or NULL.

  • If column not present ‘b’ is considered.

Where:

ANY-INTEGER

smallint, int, bigint

ANY-NUMERICAL

smallint, int, bigint, real, float

Result Columns

Column

Type

Description

seq

INTEGER

Row sequence.

path_seq

INTEGER

Relative position in the path of node and edge. Has value 1 for the beginning of a path.

path_id

INTEGER

Path identifier. The ordering of the paths: For two paths i, j if i < j then agg_cost(i) <= agg_cost(j).

node

BIGINT

Identifier of the node in the path. Negative values are the identifiers of a point.

edge

BIGINT

Identifier of the edge used to go from node to the next node in the path sequence.
  • -1 for the last row in the path sequence.

cost

FLOAT

Cost to traverse from node using edge to the next node in the path sequence.
  • 0 for the last row in the path sequence.

agg_cost

FLOAT

Aggregate cost from start_pid to node.
  • 0 for the first row in the path sequence.

Additional Examples

Example

Left side driving topology from point \(1\) to point \(2\) in \(2\) cycles, with details

SELECT * FROM pgr_withPointsKSP(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, -2, 2,
    driving_side := 'l', details := true);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |   -1 |    1 |  0.6 |        0
   2 |       1 |        2 |    2 |    4 |  0.7 |      0.6
   3 |       1 |        3 |   -6 |    4 |  0.3 |      1.3
   4 |       1 |        4 |    5 |    8 |    1 |      1.6
   5 |       1 |        5 |    6 |    9 |    1 |      2.6
   6 |       1 |        6 |    9 |   15 |    1 |      3.6
   7 |       1 |        7 |   12 |   15 |  0.6 |      4.6
   8 |       1 |        8 |   -2 |   -1 |    0 |      5.2
   9 |       2 |        1 |   -1 |    1 |  0.6 |        0
  10 |       2 |        2 |    2 |    4 |  0.7 |      0.6
  11 |       2 |        3 |   -6 |    4 |  0.3 |      1.3
  12 |       2 |        4 |    5 |    8 |    1 |      1.6
  13 |       2 |        5 |    6 |   11 |    1 |      2.6
  14 |       2 |        6 |   11 |   13 |    1 |      3.6
  15 |       2 |        7 |   12 |   15 |  0.6 |      4.6
  16 |       2 |        8 |   -2 |   -1 |    0 |      5.2
(16 rows)

Example

Right side driving topology from point \(1\) to point \(2\) in \(2\) cycles, with heap paths and details

SELECT * FROM pgr_withPointsKSP(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, -2, 2,
    heap_paths := true, driving_side := 'r', details := true);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |   -1 |    1 |  0.4 |        0
   2 |       1 |        2 |    1 |    1 |    1 |      0.4
   3 |       1 |        3 |    2 |    4 |  0.7 |      1.4
   4 |       1 |        4 |   -6 |    4 |  0.3 |      2.1
   5 |       1 |        5 |    5 |    8 |    1 |      2.4
   6 |       1 |        6 |    6 |    9 |    1 |      3.4
   7 |       1 |        7 |    9 |   15 |  0.4 |      4.4
   8 |       1 |        8 |   -2 |   -1 |    0 |      4.8
   9 |       2 |        1 |   -1 |    1 |  0.4 |        0
  10 |       2 |        2 |    1 |    1 |    1 |      0.4
  11 |       2 |        3 |    2 |    4 |  0.7 |      1.4
  12 |       2 |        4 |   -6 |    4 |  0.3 |      2.1
  13 |       2 |        5 |    5 |    8 |    1 |      2.4
  14 |       2 |        6 |    6 |   11 |    1 |      3.4
  15 |       2 |        7 |   11 |   13 |    1 |      4.4
  16 |       2 |        8 |   12 |   15 |    1 |      5.4
  17 |       2 |        9 |    9 |   15 |  0.4 |      6.4
  18 |       2 |       10 |   -2 |   -1 |    0 |      6.8
  19 |       3 |        1 |   -1 |    1 |  0.4 |        0
  20 |       3 |        2 |    1 |    1 |    1 |      0.4
  21 |       3 |        3 |    2 |    4 |  0.7 |      1.4
  22 |       3 |        4 |   -6 |    4 |  0.3 |      2.1
  23 |       3 |        5 |    5 |   10 |    1 |      2.4
  24 |       3 |        6 |   10 |   12 |  0.6 |      3.4
  25 |       3 |        7 |   -3 |   12 |  0.4 |        4
  26 |       3 |        8 |   11 |   13 |    1 |      4.4
  27 |       3 |        9 |   12 |   15 |    1 |      5.4
  28 |       3 |       10 |    9 |   15 |  0.4 |      6.4
  29 |       3 |       11 |   -2 |   -1 |    0 |      6.8
(29 rows)

The queries use the Sample Data network.