pgr_lineGraph  Experimental¶
pgr_lineGraph
— Transforms a given graph into its corresponding edgebased graph.
Warning
Possible server crash
These functions might create a server crash
Warning
Experimental functions
They are not officially of the current release.
They likely will not be officially be part of the next release:
The functions might not make use of ANYINTEGER and ANYNUMERICAL
Name might change.
Signature might change.
Functionality might change.
pgTap tests might be missing.
Might need c/c++ coding.
May lack documentation.
Documentation if any might need to be rewritten.
Documentation examples might need to be automatically generated.
Might need a lot of feedback from the comunity.
Might depend on a proposed function of pgRouting
Might depend on a deprecated function of pgRouting
Availability
Version 2.5.0
New Experimental function
Support
Description¶
Given a graph G, its line graph L(G) is a graph such that:
Each vertex of L(G) represents an edge of G
Two vertices of L(G) are adjacent if and only if their corresponding edges share a common endpoint in G.
Signatures¶
Summary
pgr_lineGraph(edges_sql, directed)
RETURNS SET OF (seq, source, target, cost, reverse_cost)
OR EMPTY SET
Using defaults
pgr_lineGraph(edges_sql)
RETURNS SET OF (seq, source, target, cost, reverse_cost) OR EMPTY SET
 Example
For a directed graph
SELECT * FROM pgr_lineGraph(
'SELECT id, source, target, cost, reverse_cost FROM edge_table'
);
seq  source  target  cost  reverse_cost
++++
1  18  18  1  1
2  17  17  1  1
3  16  3  1  1
4  16  16  1  1
5  15  9  1  1
6  15  15  1  1
7  14  10  1  1
8  14  12  1  1
9  14  14  1  1
10  10  7  1  1
11  10  4  1  1
12  10  8  1  1
13  10  10  1  1
14  9  8  1  1
15  9  9  1  1
16  9  11  1  1
17  8  7  1  1
18  8  4  1  1
19  8  8  1  1
20  7  6  1  1
21  6  6  1  1
22  4  1  1  1
23  4  4  1  1
24  3  2  1  1
25  3  5  1  1
26  2  1  1  1
27  2  4  1  1
28  1  1  1  1
29  5  8  1  1
30  5  9  1  1
31  5  11  1  1
32  7  7  1  1
33  7  4  1  1
34  8  11  1  1
35  10  12  1  1
36  11  13  1  1
37  12  13  1  1
38  13  15  1  1
39  16  9  1  1
40  16  15  1  1
(40 rows)
Complete Signature¶
pgr_lineGraph(edges_sql, directed);
RETURNS SET OF (seq, source, target, cost, reverse_cost) OR EMPTY SET
 Example
For an undirected graph
SELECT * FROM pgr_lineGraph(
'SELECT id, source, target, cost, reverse_cost FROM edge_table',
FALSE
);
seq  source  target  cost  reverse_cost
++++
1  3  2  1  1
2  3  5  1  1
3  2  4  1  1
4  1  4  1  1
5  4  8  1  1
6  4  10  1  1
7  5  9  1  1
8  5  11  1  1
9  6  7  1  1
10  7  8  1  1
11  7  10  1  1
12  8  9  1  1
13  8  11  1  1
14  9  15  1  1
15  10  12  1  1
16  10  14  1  1
17  11  13  1  1
18  12  13  1  1
19  16  15  1  1
(19 rows)
Parameters¶
Column 
Type 
Description 

edges_sql 

SQL query as described above. 
directed 


Inner 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
Result Columns¶
RETURNS SETOF (seq, source, target, cost, reverse_cost)
Column 
Type 
Description 

seq 

Sequential value starting from 1. 
source 

Identifier of the source vertex of the current edge id.

target 

Identifier of the target vertex of the current edge id.

cost 

Weight of the edge (source, target).

reverse_cost 

Weight of the edge (target, source).
