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

Indices and tables