# pgRouting Manual (2.5)

## pgr_dijkstraCostMatrix - proposed

## Name

`pgr_dijkstraCostMatrix` - Calculates the a cost matrix using pgr_dijktras.

Warning

Proposed functions for next mayor release.

- They are not officially in the current release.
- They will likely officially be part of the next mayor release:
  - The functions make use of ANY-INTEGER and ANY-NUMERICAL
  - Name might not change. (But still can)
  - Signature might not change. (But still can)
  - Functionality might not change. (But still can)
  - pgTap tests have being done. But might need more.
  - Documentation might need refinement.

Boost Graph Inside

Availability: 2.3.0

## Synopsis

Using Dijkstra algorithm, calculate and return a cost matrix.

## Signature Summary

    pgr_dijkstraCostMatrix(edges_sql, start_vids)
    pgr_dijkstraCostMatrix(edges_sql, start_vids, directed)
    RETURNS SET OF (start_vid, end_vid, agg_cost)

## Signatures

### Minimal Signature

The minimal signature:
  - Is for a directed graph.

    pgr_dijkstraCostMatrix(edges_sql, start_vid)
    RETURNS SET OF (start_vid, end_vid, agg_cost)

Example: | Cost matrix for vertices 1, 2, 3, and 4.

    SELECT * FROM pgr_dijkstraCostMatrix(
        '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_dijkstraCostMatrix(edges_sql, start_vids, directed:=true)
    RETURNS SET OF (start_vid, end_vid, agg_cost)

Example: | Cost matrix for an undirected graph for vertices 1, 2, 3, and 4.

This example returns a symmetric cost matrix.

    SELECT * FROM pgr_dijkstraCostMatrix(
        '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)

## Description of the Signatures

### Description of the edges_sql query for dijkstra like functions

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

### Description of the parameters of the signatures

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.

### Description of the return values for a Cost function

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`.

## Examples

Example: | Use with tsp

    SELECT * FROM pgr_TSP(
        $$
        SELECT * FROM pgr_dijkstraCostMatrix(
            'SELECT id, source, target, cost, reverse_cost FROM edge_table',
            (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
            false
        )
        $$,
        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

- Dijkstra - Family of functions
- Cost Matrix - Category
- Traveling Sales Person - Family of functions
- The queries use the Sample Data network.

Indices and tables

- Index
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