pgr_dijkstraVia  Proposed¶
Name¶
pgr_dijkstraVia — Using dijkstra algorithm, it finds the route that goes through a list of vertices.
Synopsis¶
Given a list of vertices and a graph, this function is equivalent to finding the shortest path between \(vertex_i\) and \(vertex_{i+1}\) for all \(i < size\_of(vertex_via)\).
The paths represents the sections of the route.
Note
This is a proposed function
Signatrue Summary¶
pgr_dijkstraVia(edges_sql, via_vertices)
pgr_dijkstraVia(edges_sql, via_vertices, directed, strict, U_turn_on_edge)
RETURNS SET OF (seq, path_pid, path_seq, start_vid, end_vid,
node, edge, cost, agg_cost, route_agg_cost) or EMPTY SET
Signatures¶
Minimal Signature¶
pgr_dijkstraVia(edges_sql, via_vertices)
RETURNS SET OF (seq, path_pid, path_seq, start_vid, end_vid,
node, edge, cost, agg_cost, route_agg_cost) or EMPTY SET
Example:  Find the route that visits the vertices 1 3 9 in that order 

SELECT * FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 3, 9]
);
seq  path_id  path_seq  start_vid  end_vid  node  edge  cost  agg_cost  route_agg_cost
+++++++++
1  1  1  1  3  1  1  1  0  0
2  1  2  1  3  2  4  1  1  1
3  1  3  1  3  5  8  1  2  2
4  1  4  1  3  6  9  1  3  3
5  1  5  1  3  9  16  1  4  4
6  1  6  1  3  4  3  1  5  5
7  1  7  1  3  3  1  0  6  6
8  2  1  3  9  3  5  1  0  6
9  2  2  3  9  6  9  1  1  7
10  2  3  3  9  9  2  0  2  8
(10 rows)
Complete Signature¶
pgr_dijkstraVia(edges_sql, via_vertices, directed, strict, U_turn_on_edge)
RETURNS SET OF (seq, path_pid, path_seq, start_vid, end_vid,
node, edge, cost, agg_cost, route_agg_cost) or EMPTY SET
Example:  Find the route that visits the vertices 1 3 9 in that order on an undirected graph, avoiding Uturns when possible 

SELECT * FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 3, 9], false, strict:=true, U_turn_on_edge:=false
);
seq  path_id  path_seq  start_vid  end_vid  node  edge  cost  agg_cost  route_agg_cost
+++++++++
1  1  1  1  3  1  1  1  0  0
2  1  2  1  3  2  2  1  1  1
3  1  3  1  3  3  1  0  2  2
4  2  1  3  9  3  5  1  0  2
5  2  2  3  9  6  9  1  1  3
6  2  3  3  9  9  2  0  2  4
(6 rows)
Description of the Signature¶
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  ANYINTEGER  Identifier of the edge.  
source  ANYINTEGER  Identifier of the first end point vertex of the edge.  
target  ANYINTEGER  Identifier of the second end point vertex of the edge.  
cost  ANYNUMERICAL 


reverse_cost  ANYNUMERICAL  1 

Where:
ANYINTEGER:  SMALLINT, INTEGER, BIGINT 

ANYNUMERICAL:  SMALLINT, INTEGER, BIGINT, REAL, FLOAT 
Description of the parameters of the signatures¶
Parameter  Type  Default  Description 

edges_sql  TEXT  SQL query as described above.  
via_vertices  ARRAY[ANYINTEGER]  Array of ordered vertices identifiers that are going to be visited.  
directed  BOOLEAN  true 

strict  BOOLEAN  false 

U_turn_on_edge  BOOLEAN  true 

Description of the parameters of the signatures¶
Parameter  Type  Description 

edges_sql  TEXT  SQL query as described above. 
via_vertices  ARRAY[ANYINTEGER]  Array of vertices identifiers 
directed  BOOLEAN  (optional) Default is true (is directed). When set to false the graph is considered as Undirected 
strict  BOOLEAN  (optional) ignores if a subsection of the route is missing and returns everything it found Default is true (is directed). When set to false the graph is considered as Undirected 
U_turn_on_edge  BOOLEAN  (optional) Default is true (is directed). When set to false the graph is considered as Undirected 
Description of the return values¶
Returns set of (start_vid, end_vid, agg_cost)
Column  Type  Description 

seq  BIGINT  Sequential value starting from 1. 
path_pid  BIGINT  Identifier of the path. 
path_seq  BIGINT  Sequential value starting from 1 for the path. 
start_vid  BIGINT  Identifier of the starting vertex of the path. 
end_vid  BIGINT  Identifier of the ending vertex of the path. 
node  BIGINT  Identifier of the node in the path from start_vid to end_vid. 
edge  BIGINT  Identifier of the edge used to go from node to the next node in the path sequence. 1 for the last node of the path. 2 for the last node of the route. 
cost  FLOAT  Cost to traverse from node using edge to the next node in the route sequence. 
agg_cost  FLOAT  Total cost from start_vid to end_vid of the path. 
route_agg_cost  FLOAT  Total cost from start_vid of path_pid = 1 to end_vid of the current path_pid . 
Examples¶
Example 1:  Find the route that visits the vertices 1 5 3 9 4 in that order 

SELECT * FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4]
);
seq  path_id  path_seq  start_vid  end_vid  node  edge  cost  agg_cost  route_agg_cost
+++++++++
1  1  1  1  5  1  1  1  0  0
2  1  2  1  5  2  4  1  1  1
3  1  3  1  5  5  1  0  2  2
4  2  1  5  3  5  8  1  0  2
5  2  2  5  3  6  9  1  1  3
6  2  3  5  3  9  16  1  2  4
7  2  4  5  3  4  3  1  3  5
8  2  5  5  3  3  1  0  4  6
9  3  1  3  9  3  5  1  0  6
10  3  2  3  9  6  9  1  1  7
11  3  3  3  9  9  1  0  2  8
12  4  1  9  4  9  16  1  0  8
13  4  2  9  4  4  2  0  1  9
(13 rows)
Example 2:  What’s the aggregate cost of the third path? 

SELECT agg_cost FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4]
)
WHERE path_id = 3 AND edge <0;
agg_cost

2
(1 row)
Example 3:  What’s the route’s aggregate cost of the route at the end of the third path? 

SELECT route_agg_cost FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4]
)
WHERE path_id = 3 AND edge < 0;
route_agg_cost

8
(1 row)
Example 4:  How are the nodes visited in the route? 

SELECT row_number() over () as node_seq, node
FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4]
)
WHERE edge <> 1 ORDER BY seq;
node_seq  node
+
1  1
2  2
3  5
4  6
5  9
6  4
7  3
8  6
9  9
10  4
(10 rows)
Example 5:  What are the aggregate costs of the route when the visited vertices are reached? 

SELECT path_id, route_agg_cost FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4]
)
WHERE edge < 0;
path_id  route_agg_cost
+
1  2
2  6
3  8
4  9
(4 rows)
Example 6:  show the route’s seq and aggregate cost and a status of “passes in front” or “visits” node 9 

SELECT seq, route_agg_cost, node, agg_cost ,
CASE WHEN edge = 1 THEN 'visits'
ELSE 'passes in front'
END as status
FROM pgr_dijkstraVia(
'SELECT id, source, target, cost, reverse_cost FROM edge_table order by id',
ARRAY[1, 5, 3, 9, 4])
WHERE node = 9 and (agg_cost <> 0 or seq = 1);
seq  route_agg_cost  node  agg_cost  status
++++
6  4  9  2  passes in front
11  8  9  2  visits
(2 rows)
See Also¶
Indices and tables