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

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 cycles,
  [, directed] [,heap_paths] [, stop_on_first] [,strict])
RETURNS SETOF (seq, path_id, path_seq, node, edge, cost, agg_cost)
Example:From vertex \(3\) to vertex \(8\) on a directed graph 
SELECT * FROM pgr_turnRestrictedPath(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM new_restrictions$$,
  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(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM new_restrictions$$,
  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(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM new_restrictions$$,
  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(
  $$SELECT id, source, target, cost, reverse_cost FROM edges$$,
  $$SELECT path, cost FROM new_restrictions$$,
  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)