pgr_dijkstraNear  Proposed  pgRouting Manual (3.3)
pgr_dijkstraNear  Proposed
pgr_dijkstraNear
 Using dijkstra algorithm, finds the route that leads to
the nearest vertex.
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 ANYINTEGER and ANYNUMERICAL

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.

Availability

Version 3.3.0

Promoted to proposed function


Version 3.2.0

New experimental function

Description
Given a graph, a starting vertex and a set of ending vertices, this function finds the shortest path from the starting vertex to the nearest ending vertex.
Characteristics

Uses Dijkstra algorithm.

Works for directed and undirected graphs.

When there are more than one path to the same vertex with same cost:

The algorithm will return just one path


Optionally allows to find more than one path.

When more than one path is to be returned:

Results are sorted in increasing order of:

aggregate cost

Within the same value of aggregate costs:

results are sorted by (source, target)





Running time: Dijkstra running time: \(drt = O((E + V)logV)\)

One to Many; \(drt\)

Many to One: \(drt\)

Many to Many: \(drt * Starting vids\)

Combinations: \(drt * Starting vids\)

Signatures
Summary
pgr_dijkstraNear(Edges SQL, Start vid, End vids [, directed] [, cap])
pgr_dijkstraNear(Edges SQL, Start vids, End vid [, directed] [, cap])
pgr_dijkstraNear(Edges SQL, Start vids, End vids [, directed] [, cap], [global])
pgr_dijkstraNear(Edges SQL, Combinations SQL [, directed] [, cap], [global])
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)
OR EMPTY SET
One to Many
pgr_dijkstraNear(Edges SQL, Start vid, End vids [, directed] [, cap])
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)
OR EMPTY SET
 Example :

Departing on car from vertex \(2\) find the nearest subway station.

Using a directed graph for car routing.

The subway stations are on the following vertices \(\{ 3, 6, 7\}\)

The defaults used:

directed => true

cap => 1

1SELECT * FROM pgr_dijkstraNear(
2 'SELECT id, source, target, cost, reverse_cost FROM edge_table',
3 2, ARRAY[3, 6, 7]
4);
5 seq path_seq start_vid end_vid node edge cost agg_cost
6+++++++
7 1 1 2 6 2 4 1 0
8 2 2 2 6 5 8 1 1
9 3 3 2 6 6 1 0 2
10(3 rows)
11
The result shows that station at vertex \(6\) is the nearest.
Many to One
pgr_dijkstraNear(Edges SQL, Start vids, End vid [, directed] [, cap])
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)
OR EMPTY SET
 Example :

Departing on a car from a subway station find the nearest two stations to vertex \(2\)

Using a directed graph for car routing.

The subway stations are on the following vertices \(\{ 3, 6, 7\}\)

On line 4 : using the positional parameter: directed set to
true

In line 5 : using named parameter cap => 2
1SELECT * FROM pgr_dijkstraNear(
2 'SELECT id, source, target, cost, reverse_cost FROM edge_table',
3 ARRAY[3, 6, 7], 2,
4 true,
5 cap => 2
6);
7 seq path_seq start_vid end_vid node edge cost agg_cost
8+++++++
9 1 1 3 2 3 2 1 0
10 2 2 3 2 2 1 0 1
11 3 1 6 2 6 8 1 0
12 4 2 6 2 5 4 1 1
13 5 3 6 2 2 1 0 2
14(5 rows)
15
The result shows that station at vertex \(3\) is the nearest and the next best is \(6\) .
Many to Many
pgr_dijkstraNear(Edges SQL, Start vids, End vids [, directed] [, cap], [global])
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)
OR EMPTY SET
 Example :

Find the best pedestrian connection between two lines of buses

Unsing an undirected graph for pedestrian routing

The first subway line stations stops are at \(\{3, 6, 7\}\)

The second subway line stations are at \(\{4, 9\}\)

On line 4 : using the named parameter: directed => false

The defaults used:

cap => 1

global => true

1SELECT * FROM pgr_dijkstraNear(
2 'SELECT id, source, target, cost, reverse_cost FROM edge_table',
3 ARRAY[4, 9], ARRAY[3, 6, 7],
4 directed => false
5);
6 seq path_seq start_vid end_vid node edge cost agg_cost
7+++++++
8 1 1 4 3 4 3 1 0
9 2 2 4 3 3 1 0 1
10(2 rows)
11
For a pedestrian the best connection is to get on/off is at vertex \(3\) of the first subway line and at vertex \(4\) of the second subway line.
Only
one
route is returned because
global
is
true
and
cap
is
1
Combinations
pgr_dijkstraNear(Edges SQL, Combinations SQL [, directed] [, cap], [global])
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost)
OR EMPTY SET
 Example :

Find the best car connection between all the stations of two subway lines

Using a directed graph for car routing.

The first subway line stations stops are at \(\{3, 6, 7\}\)

The second subway line stations are at \(\{4, 9\}\)

line 3 sets the start vertices to be from the fisrt subway line and the ending vertices to be from the second subway line

line 5 sets the start vertices to be from the first subway line and the ending vertices to be from the first subway line

On line 6 : using the named parameter is global => false

The defaults used:

directed => true

cap => 1

1SELECT * FROM pgr_dijkstraNear(
2 'SELECT id, source, target, cost, reverse_cost FROM edge_table',
3 'SELECT unnest(ARRAY[3, 6, 7]) as source, target FROM (SELECT unnest(ARRAY[4, 9]) AS target) a
4 UNION
5 SELECT unnest(ARRAY[4, 9]), target FROM (SELECT unnest(ARRAY[3, 6, 7]) AS target) b',
6 global => false
7);
8 seq path_seq start_vid end_vid node edge cost agg_cost
9+++++++
10 1 1 4 3 4 3 1 0
11 2 2 4 3 3 1 0 1
12 3 1 6 9 6 9 1 0
13 4 2 6 9 9 1 0 1
14 5 1 9 6 9 9 1 0
15 6 2 9 6 6 1 0 1
16 7 1 3 9 3 5 1 0
17 8 2 3 9 6 9 1 1
18 9 3 3 9 9 1 0 2
19 10 1 7 9 7 6 1 0
20 11 2 7 9 8 7 1 1
21 12 3 7 9 5 8 1 2
22 13 4 7 9 6 9 1 3
23 14 5 7 9 9 1 0 4
24(14 rows)
25
From the results:

making a connection from the first subway line to the second:

\({(3 > 9) (6 > 9) (7 > 9)}\) and the best one is \((6 > 9)\) with a cost of \(1\) (lines: 12 and 13 )


making a connection from the second subway line to the first:

\({(4 > 3) (9 > 6)}\) and both are equaly good as they have the same cost. (lines: 10 and 11 and lines: 14 and 15 )

Parameters
Parameter 
Type 
Default 
Description 

Edges SQL 

Edges query as described below 

Combinations SQL 

Combinations query as described below 

Start vid 

Identifier of the starting vertex of the path. 

Start vids 

Array of identifiers of starting vertices. 

End vid 

Identifier of the ending vertex of the path. 

End vids 

Array of identifiers of ending vertices. 

directed 



cap 

1 
Find at most

global 



Inner query
Edges query
Column 
Type 
Default 
Description 

id 

Identifier of the edge. 

source 

Identifier of the first end point vertex of the edge. 

target 

Identifier of the second end point vertex of the edge. 

cost 

Weight of the edge (source, target)


reverse_cost 

1 
Weight of the edge (target, source) ,

Where:
 ANYINTEGER :

SMALLINT, INTEGER, BIGINT
 ANYNUMERICAL :

SMALLINT, INTEGER, BIGINT, REAL, FLOAT
Combinations query
Column 
Type 
Default 
Description 

source 

Identifier of the first end point vertex of the edge. 

target 

Identifier of the second end point vertex of the edge. 
Where:
 ANYINTEGER :

SMALLINT, INTEGER, BIGINT
Return Columns
RETURNS SET OF
(seq,
path_seq,
start_vid,
end_vid,
node,
edge,
cost,
agg_cost)
OR EMPTY SET
Column 
Type 
Description 

seq 

Sequential value starting from 1. 
path_seq 

Sequential value starting from 1 for each \((start\_vid \to end\_vid)\) path. 
start_vid 

Identifier of the starting vertex of the path. 
end_vid 

Identifier of the ending vertex of the path. 
node 

Identifier of the node at position

edge 

Identifier of the edge used to go from node at

cost 

Cost to traverse from

agg_cost 

Total cost of traversing \((start\_vid \to node)\) section of the \((start\_vid \to end\_vid)\) path. 
See Also

Sample Data network.

boost: https://www.boost.org/libs/graph/doc/table_of_contents.html

Wikipedia: https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
Indices and tables