Database

pgrouting: Geospatial Routing

pgRouting is Postgres and PostGIS extension adding geospatial routing functionality.

The core functionality of pgRouting is a set of path finding algorithms including:

  • All Pairs Shortest Path, Johnson’s Algorithm
  • All Pairs Shortest Path, Floyd-Warshall Algorithm
  • Shortest Path A*
  • Bi-directional Dijkstra Shortest Path
  • Bi-directional A* Shortest Path
  • Shortest Path Dijkstra
  • Driving Distance
  • K-Shortest Path, Multiple Alternative Paths
  • K-Dijkstra, One to Many Shortest Path
  • Traveling Sales Person
  • Turn Restriction Shortest Path (TRSP)

Enable the extension

  1. Go to the Database page in the Dashboard.
  2. Click on Extensions in the sidebar.
  3. Search for pgrouting and enable the extension.

Example

As an example, we'll solve the traveling salesperson problem using the pgRouting's pgr_TSPeuclidean function from some PostGIS coordinates.

A summary of the traveling salesperson problem is, given a set of city coordinates, solve for a path that goes through each city and minimizes the total distance traveled.

First we populate a table with some X, Y coordinates

1
create table wi29 (
2
  id bigint,
3
  x float,
4
  y float,
5
  geom gis.geometry
6
);
7
8
insert into wi29 (id, x, y)
9
values
10
  (1,20833.3333,17100.0000),
11
  (2,20900.0000,17066.6667),
12
  (3,21300.0000,13016.6667),
13
  (4,21600.0000,14150.0000),
14
  (5,21600.0000,14966.6667),
15
  (6,21600.0000,16500.0000),
16
  (7,22183.3333,13133.3333),
17
  (8,22583.3333,14300.0000),
18
  (9,22683.3333,12716.6667),
19
  (10,23616.6667,15866.6667),
20
  (11,23700.0000,15933.3333),
21
  (12,23883.3333,14533.3333),
22
  (13,24166.6667,13250.0000),
23
  (14,25149.1667,12365.8333),
24
  (15,26133.3333,14500.0000),
25
  (16,26150.0000,10550.0000),
26
  (17,26283.3333,12766.6667),
27
  (18,26433.3333,13433.3333),
28
  (19,26550.0000,13850.0000),
29
  (20,26733.3333,11683.3333),
30
  (21,27026.1111,13051.9444),
31
  (22,27096.1111,13415.8333),
32
  (23,27153.6111,13203.3333),
33
  (24,27166.6667,9833.3333),
34
  (25,27233.3333,10450.0000),
35
  (26,27233.3333,11783.3333),
36
  (27,27266.6667,10383.3333),
37
  (28,27433.3333,12400.0000),
38
  (29,27462.5000,12992.2222);

Next we use the pgr_TSPeuclidean function to find the best path.

1
select
2
    *
3
from
4
     pgr_TSPeuclidean($$select * from wi29$$)
1
seq | node |       cost       |     agg_cost     
2
-----+------+------------------+------------------
3
   1 |    1 |                0 |                0
4
   2 |    2 |  74.535614157127 |  74.535614157127
5
   3 |    6 | 900.617093380362 | 975.152707537489
6
   4 |   10 | 2113.77757765045 | 3088.93028518793
7
   5 |   11 | 106.718669615254 | 3195.64895480319
8
   6 |   12 | 1411.95293791574 | 4607.60189271893
9
   7 |   13 | 1314.23824873744 | 5921.84014145637
10
   8 |   14 | 1321.76283931305 | 7243.60298076942
11
   9 |   17 | 1202.91366735569 |  8446.5166481251
12
  10 |   18 | 683.333268292684 | 9129.84991641779
13
  11 |   15 | 1108.05137466134 | 10237.9012910791
14
  12 |   19 | 772.082339448903 |  11009.983630528
15
  13 |   22 | 697.666150054665 | 11707.6497805827
16
  14 |   23 | 220.141999627513 | 11927.7917802102
17
  15 |   21 | 197.926372783442 | 12125.7181529937
18
  16 |   29 | 440.456596290771 | 12566.1747492844
19
  17 |   28 | 592.939989005405 | 13159.1147382898
20
  18 |   26 | 648.288376333318 | 13807.4031146231
21
  19 |   20 | 509.901951359278 | 14317.3050659824
22
  20 |   25 | 1330.83095428717 | 15648.1360202696
23
  21 |   27 |  74.535658878487 | 15722.6716791481
24
  22 |   24 | 559.016994374947 |  16281.688673523
25
  23 |   16 | 1243.87392358622 | 17525.5625971092
26
  24 |    9 |  4088.0585364911 | 21613.6211336004
27
  25 |    7 |  650.85409697993 | 22264.4752305803
28
  26 |    3 | 891.004385199336 | 23155.4796157796
29
  27 |    4 | 1172.36699411442 |  24327.846609894
30
  28 |    8 | 994.708187806297 | 25322.5547977003
31
  29 |    5 | 1188.01888359478 | 26510.5736812951
32
  30 |    1 | 2266.91173136004 | 28777.4854126552

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