1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
BEGIN;
BEGIN
SET client_min_messages TO NOTICE;
SET
/* :file: This file is part of the pgRouting project.
:copyright: Copyright (c) 2018-2026 pgRouting developers
:license: Creative Commons Attribution-Share Alike 3.0 https://creativecommons.org/licenses/by-sa/3.0 */
/* -- q1 */
SELECT * FROM pgr_topologicalsort(
$$SELECT id, source, target, cost
FROM edges WHERE cost >= 0
UNION
SELECT id, target, source, reverse_cost
FROM edges WHERE cost < 0$$);
seq | node
-----+------
1 | 1
2 | 5
3 | 2
4 | 4
5 | 3
6 | 13
7 | 14
8 | 15
9 | 10
10 | 6
11 | 7
12 | 8
13 | 9
14 | 11
15 | 16
16 | 12
17 | 17
(17 rows)
/* -- q2 */
SELECT * FROM pgr_topologicalsort(
$$SELECT id, source, target, cost, -1 AS reverse_cost
FROM edges WHERE cost >= 0
UNION
SELECT id, source, target, -1, reverse_cost
FROM edges WHERE cost < 0$$);
seq | node
-----+------
1 | 5
2 | 2
3 | 4
4 | 13
5 | 14
6 | 1
7 | 3
8 | 15
9 | 10
10 | 6
11 | 7
12 | 8
13 | 9
14 | 11
15 | 12
16 | 16
17 | 17
(17 rows)
/* -- q3 */
SELECT * FROM pgr_topologicalsort(
$$SELECT id, source, target, cost, reverse_cost FROM edges$$);
ERROR: Graph is not DAG
CONTEXT: SQL function "pgr_topologicalsort" statement 1
/* -- q4 */
ROLLBACK;
ROLLBACK
|
