pgr_bdDijkstraCostMatrix

pgr_bdDijkstraCostMatrix - Calculates the a cost matrix using pgr_bdDijkstra.

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Boost Graph Inside

Availability:

  • Official on v3.0.0
  • Proposed on v2.5.0

Description

Using Dijkstra algorithm, calculate and return 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

edges_sql:an SQL query, which should return a set of rows with the following columns:
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. Used when multiple starting vetrices are in the query.
end_vid BIGINT Identifier of the ending vertex. Used when multiple ending vertices are in the query.
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