# pgr_bdDijkstraCostMatrix¶

pgr_bdDijkstraCostMatrix - Calculates the a cost matrix using pgr_bdDijkstra.

Availability:

• Version 3.0.0

• Official function

• Version 2.5.0

• New proposed function

## 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.

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 |    0 |        0
2 |    2 |    1 |        1
3 |    3 |    1 |        2
4 |    4 |    1 |        3
5 |    1 |    3 |        6
(5 rows)