pgr_dijkstraCostMatrix - proposed¶
Name¶
pgr_dijkstraCostMatrix - Calculates the a cost matrix using pgr_dijktras.
Warning
These are 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.
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¶
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 |
|
|
reverse_cost | ANY-NUMERICAL | -1 |
|
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¶
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 of the shortest path 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
- Traveling Sales Person
- The queries use the Sample Data network.
Indices and tables