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.

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 |  0.4 |        0
|       1 |        2 |    1 |    1 |    1 |      0.4
|       1 |        3 |    2 |    4 |  0.7 |      1.4
|       1 |        4 |   -6 |    4 |  0.3 |      2.1
|       1 |        5 |    5 |    8 |    1 |      2.4
|       1 |        6 |    6 |    9 |    1 |      3.4
|       1 |        7 |    9 |   15 |  0.4 |      4.4
|       1 |        8 |   -2 |   -1 |    0 |      4.8
|       2 |        1 |   -1 |    1 |  0.4 |        0
|       2 |        2 |    1 |    1 |    1 |      0.4
|       2 |        3 |    2 |    4 |  0.7 |      1.4
|       2 |        4 |   -6 |    4 |  0.3 |      2.1
|       2 |        5 |    5 |    8 |    1 |      2.4
|       2 |        6 |    6 |   11 |    1 |      3.4
|       2 |        7 |   11 |   13 |    1 |      4.4
|       2 |        8 |   12 |   15 |    1 |      5.4
|       2 |        9 |    9 |   15 |  0.4 |      6.4
|       2 |       10 |   -2 |   -1 |    0 |      6.8
|       3 |        1 |   -1 |    1 |  0.4 |        0
|       3 |        2 |    1 |    1 |    1 |      0.4
|       3 |        3 |    2 |    4 |  0.7 |      1.4
|       3 |        4 |   -6 |    4 |  0.3 |      2.1
|       3 |        5 |    5 |   10 |    1 |      2.4
|       3 |        6 |   10 |   12 |  0.6 |      3.4
|       3 |        7 |   -3 |   12 |  0.4 |        4
|       3 |        8 |   11 |   13 |    1 |      4.4
|       3 |        9 |   12 |   15 |    1 |      5.4
|       3 |       10 |    9 |   15 |  0.4 |      6.4
|       3 |       11 |   -2 |   -1 |    0 |      6.8
(29 rows)

The queries use the Sample Data network.