pgr_bdDijkstraCostMatrix - proposed¶
Name¶
pgr_bdDijkstraCostMatrix
- Calculates the a cost matrix using pgr_bdDijkstra.
Availability: 2.5.0
Warning
Experimental functions
- They are not officially of the current release.
- They likely will not be officially be part of the next release:
- The functions might not make use of ANY-INTEGER and ANY-NUMERICAL
- Name might change.
- Signature might change.
- Functionality might change.
- pgTap tests might be missing.
- Might need c/c++ coding.
- May lack documentation.
- Documentation if any might need to be rewritten.
- Documentation examples might need to be automatically generated.
- Might need a lot of feedback from the comunity.
- Might depend on a proposed function of pgRouting
- Might depend on a deprecated function of pgRouting
Synopsis¶
Using Dijkstra algorithm, calculate and return a cost matrix.
Signature Summary¶
pgr_bdDijkstraCostMatrix(edges_sql, start_vids)
pgr_bdDijkstraCostMatrix(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_bdDijkstraCostMatrix(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_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:=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_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)
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)
|
|
reverse_cost | ANY-NUMERICAL |
-1 | Weight of the edge (target, source),
|
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(
$$
SELECT * FROM pgr_bdDijkstraCostMatrix(
'SELECT id, source, target, cost, reverse_cost FROM edge_table',
(SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
false
)
$$,
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¶
- Bidirectional Dijkstra - Family of functions
- Cost Matrix - Category
- Traveling Sales Person - Family of functions
- The queries use the Sample Data network.
Indices and tables