pgr_turnRestrictedPath - Experimental

pgr_turnRestrictedPath Using Yen’s algorithm Vertex -Vertex routing with restrictions

Warning

Possible server crash

• These functions might create a server crash

Warning

Experimental functions

• They are not officially of the current release.

• They likely will not be officially be part of the next release:

  • The functions might not make use of ANY-INTEGER and ANY-NUMERICAL

  • Name might change.

  • Signature might change.

  • Functionality might change.

  • pgTap tests might be missing.

  • Might need c/c++ coding.

  • May lack documentation.

  • Documentation if any might need to be rewritten.

  • Documentation examples might need to be automatically generated.

  • Might need a lot of feedback from the comunity.

  • Might depend on a proposed function of pgRouting

  • Might depend on a deprecated function of pgRouting

Availability

• Version 3.0.0

  • New experimental function

Description

Using Yen’s algorithm to obtain K shortest paths and analyze the paths to select the paths that do not use the restrictions

Signatures

pgr_turnRestrictedPath(Edges SQL, Restrictions SQL, start vid, end vid, K, [options])

options: [directed, heap_paths, stop_on_first, strict]

RETURNS SET OF (seq, path_id, path_seq, node, edge, cost, agg_cost)

OR EMPTY SET

Example:

From vertex \(3\) to vertex \(8\) on a directed graph

SELECT * FROM pgr_turnRestrictedPath(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM restrictions$$,
  3, 8, 3);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |    3 |    7 |    1 | Infinity
   2 |       1 |        2 |    7 |   10 |    1 |        1
   3 |       1 |        3 |    8 |   -1 |    0 |        2
(3 rows)

Parameters

Column	Type	Description
Edges SQL	TEXT	SQL query as described.
start vid	ANY-INTEGER	Identifier of the departure vertex.
end vid	ANY-INTEGER	Identifier of the departure vertex.
K	ANY-INTEGER	Number of required paths

Where:

ANY-INTEGER:

SMALLINT, INTEGER, BIGINT

Optional parameters

Column	Type	Default	Description
directed	BOOLEAN	true	When true the graph is considered Directed When false the graph is considered as Undirected.

KSP Optional parameters

Column	Type	Default	Description
heap_paths	BOOLEAN	false	When false Returns at most K paths When true all the calculated paths while processing are returned. Roughly, when the shortest path has N edges, the heap will contain about than N * K paths for small value of K and K > 5.

Special optional parameters

Column	Type	Default	Description
stop_on_first	BOOLEAN	true	When true stops on first path found that dos not violate restrictions When false returns at most K paths
strict	BOOLEAN	false	When true returns only paths that do not violate restrictions When false returns the paths found

Inner Queries

Edges SQL

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)
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

Restrictions SQL

Column	Type	Description
path	ARRAY [ANY-INTEGER]	Sequence of edge identifiers that form a path that is not allowed to be taken. - Empty arrays or NULL arrays are ignored. - Arrays that have a NULL element will raise an exception.
Cost	ANY-NUMERICAL	Cost of taking the forbidden path.

Where:

ANY-INTEGER:

SMALLINT, INTEGER, BIGINT

ANY-NUMERICAL:

SMALLINT, INTEGER, BIGINT, REAL, FLOAT

Result Columns

Returns set of (seq, path_id, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)

Column	Type	Description
seq	INTEGER	Sequential value starting from 1.
path_id	INTEGER	Path identifier. Has value 1 for the first of a path from start_vid to end_vid.
path_seq	INTEGER	Relative position in the path. Has value 1 for the beginning of a path.
start_vid	BIGINT	Identifier of the starting vertex.
end_vid	BIGINT	Identifier of the ending vertex.
node	BIGINT	Identifier of the node in the path from start_vid to end_vid.
edge	BIGINT	Identifier of the edge used to go from node to the next node in the path sequence. -1 for the last node of the path.
cost	FLOAT	Cost to traverse from node using edge to the next node in the path sequence.
agg_cost	FLOAT	Aggregate cost from start_vid to node.

Additional Examples

Example:

From vertex \(3\) to \(8\) with strict flag on.

No results because the only path available follows a restriction.

SELECT * FROM pgr_turnRestrictedPath(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM restrictions$$,
  3, 8, 3,
  strict => true);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
(0 rows)

Example:

From vertex \(3\) to vertex \(8\) on an undirected graph

SELECT * FROM pgr_turnRestrictedPath(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM restrictions$$,
  3, 8, 3,
  directed => false);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |    3 |    7 |    1 |        0
   2 |       1 |        2 |    7 |    4 |    1 |        1
   3 |       1 |        3 |    6 |    2 |    1 |        2
   4 |       1 |        4 |   10 |    5 |    1 |        3
   5 |       1 |        5 |   11 |   11 |    1 |        4
   6 |       1 |        6 |   12 |   12 |    1 |        5
   7 |       1 |        7 |    8 |   -1 |    0 |        6
(7 rows)

Example:

From vertex \(3\) to vertex \(8\) with more alternatives

SELECT * FROM pgr_turnRestrictedPath(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM restrictions$$,
  3, 8, 3,
  directed => false,
  heap_paths => true,
  stop_on_first => false);
 seq | path_id | path_seq | node | edge | cost | agg_cost
-----+---------+----------+------+------+------+----------
   1 |       1 |        1 |    3 |    7 |    1 |        0
   2 |       1 |        2 |    7 |    4 |    1 |        1
   3 |       1 |        3 |    6 |    2 |    1 |        2
   4 |       1 |        4 |   10 |    5 |    1 |        3
   5 |       1 |        5 |   11 |   11 |    1 |        4
   6 |       1 |        6 |   12 |   12 |    1 |        5
   7 |       1 |        7 |    8 |   -1 |    0 |        6
   8 |       2 |        1 |    3 |    7 |    1 |        0
   9 |       2 |        2 |    7 |    8 |    1 |        1
  10 |       2 |        3 |   11 |    9 |    1 |        2
  11 |       2 |        4 |   16 |   15 |    1 |        3
  12 |       2 |        5 |   17 |   13 |    1 |        4
  13 |       2 |        6 |   12 |   12 |    1 |        5
  14 |       2 |        7 |    8 |   -1 |    0 |        6
(14 rows)

See Also

• K shortest paths - Category

• Sample Data

Indices and tables

• Index

• Search Page