pgr_bdAstarCostMatrix¶
pgr_bdAstarCostMatrix
- Calculates the a cost matrix using pgr_aStar.
Availability
- Version 3.0.0
- Official function
- Version 2.5.0
- New Proposed function
Support
Description¶
The main characteristics are:
- Using internaly the pgr_bdAstar algorithm
- Returns a cost matrix.
- No ordering is performed
- let v and u are nodes on the graph:
- when there is no path from v to u:
- no corresponding row is returned
- cost from v to u is \(\inf\)
- when \(v = u\) then
- no corresponding row is returned
- cost from v to u is \(0\)
- when there is no path from v to u:
- When the graph is undirected the cost matrix is symmetric
Signatures¶
Summary
pgr_bdAstarCostMatrix(edges_sql, vids [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
Using defaults
pgr_bdAstarCostMatrix(edges_sql, vids)
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_bdAstarCostMatrix(
'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 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_bdAstarCostMatrix(edges_sql, vids [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
Example: | Symmetric cost matrix for vertices \(\{1, 2, 3, 4\}\) on an undirected graph using heuristic \(2\) |
---|
SELECT * FROM pgr_bdAstarCostMatrix(
'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 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 inner query. |
vids | ARRAY[ANY-INTEGER] |
Array of vertices identifiers. |
Optional Parameters¶
Parameter | Type | Default | Description |
---|---|---|---|
directed | BOOLEAN |
true |
|
heuristic | INTEGER |
5 |
Heuristic number. Current valid values 0~5. Default
|
factor | FLOAT |
1 |
For units manipulation. \(factor > 0\). See Factor |
epsilon | FLOAT |
1 |
For less restricted results. \(epsilon >= 1\). |
Inner query¶
edges_sql¶
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),
|
x1 | ANY-NUMERICAL |
X coordinate of source vertex. | |
y1 | ANY-NUMERICAL |
Y coordinate of source vertex. | |
x2 | ANY-NUMERICAL |
X coordinate of target vertex. | |
y2 | ANY-NUMERICAL |
Y coordinate of target vertex. |
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 . |
Additional Examples¶
Example: | Use with pgr_TSP |
---|
SELECT * FROM pgr_TSP(
$$
SELECT * FROM pgr_bdAstarCostMatrix(
'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
(SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
false
)
$$,
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¶
- aStar - Family of functions
- Bidirectional A* - Family of functions
- Cost - Category
- Cost Matrix - Category
- Traveling Sales Person - Family of functions
- The queries use the Sample Data network.
Indices and tables