pgr_bdDijkstraCostMatrix

pgr_bdDijkstraCostMatrix - Calculates the a cost matrix using pgr_bdDijkstra.

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Boost Graph Inside

Availability:

  • Version 3.0.0

    • Official function

  • Version 2.5.0

    • New proposed function

  • Supported versions: current(3.1) 3.0

  • Unsupported versions: 2.6 2.5

Description

The main characteristics are:

  • Process is done only on edges with positive costs.

  • Values are returned when there is a path.

  • When the starting vertex and ending vertex are the same, there is no path.

    • The agg_cost the non included values (v, v) is 0

  • When the starting vertex and ending vertex are the different and there is no path:

    • The agg_cost the non included values (u, v) is \(\infty\)

  • Running time (worse case scenario): \(O((V \log V + E))\)

  • For large graphs where there is a path bewtween the starting vertex and ending vertex:

    • It is expected to terminate faster than pgr_dijkstra

  • Returns a cost matrix.

Signatures

Summary

pgr_bdDijkstraCostMatrix(edges_sql, start_vids [, directed])
RETURNS SET OF (start_vid, end_vid, agg_cost)

Using default

pgr_bdDijkstraCostMatrix(edges_sql, start_vid)
RETURNS SET OF (start_vid, end_vid, agg_cost)
Example

Cost matrix for vertices \(\{1, 2, 3, 4\}\) on a directed graph

SELECT * FROM pgr_bdDijkstraCostMatrix(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5)
);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         1 |       2 |        1
         1 |       3 |        6
         1 |       4 |        5
         2 |       1 |        1
         2 |       3 |        5
         2 |       4 |        4
         3 |       1 |        2
         3 |       2 |        1
         3 |       4 |        3
         4 |       1 |        3
         4 |       2 |        2
         4 |       3 |        1
(12 rows)

Complete Signature

pgr_bdDijkstraCostMatrix(edges_sql, start_vids [, directed])
RETURNS SET OF (start_vid, end_vid, agg_cost)
Example

Symmetric cost matrix for vertices \(\{1, 2, 3, 4\}\) on an undirected graph

SELECT * FROM pgr_bdDijkstraCostMatrix(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
    false
);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         1 |       2 |        1
         1 |       3 |        2
         1 |       4 |        3
         2 |       1 |        1
         2 |       3 |        1
         2 |       4 |        2
         3 |       1 |        2
         3 |       2 |        1
         3 |       4 |        1
         4 |       1 |        3
         4 |       2 |        2
         4 |       3 |        1
(12 rows)

Parameters

Parameter

Type

Description

edges_sql

TEXT

Edges SQL query as described above.

start_vids

ARRAY[ANY-INTEGER]

Array of identifiers of the vertices.

directed

BOOLEAN

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

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

Result Columns

Returns SET OF (start_vid, end_vid, agg_cost)

Column

Type

Description

start_vid

BIGINT

Identifier of the starting vertex.

end_vid

BIGINT

Identifier of the ending vertex.

agg_cost

FLOAT

Aggregate cost from start_vid to end_vid.

Additional Examples

Example

Use with tsp

SELECT * FROM pgr_TSP(
    $$
    SELECT * FROM pgr_bdDijkstraCostMatrix(
        'SELECT id, source, target, cost, reverse_cost FROM edge_table',
        (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
        false
    )
    $$,
    randomize := false
);
 seq | node | cost | agg_cost
-----+------+------+----------
   1 |    1 |    1 |        0
   2 |    2 |    1 |        1
   3 |    3 |    1 |        2
   4 |    4 |    3 |        3
   5 |    1 |    0 |        6
(5 rows)

See Also

Indices and tables