pgr_isPlanar  Experimental¶
pgr_isPlanar
— Returns a boolean depending upon the planarity of the graph.
Advertencia
Possible server crash
These functions might create a server crash
Advertencia
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 3.2.0
New experimental function
Support
Supported versions: current(3.2)
Description¶
A graph is planar if it can be drawn in twodimensional space with no two of its edges crossing. Such a drawing of a planar graph is called a plane drawing. Every planar graph also admits a straightline drawing, which is a plane drawing where each edge is represented by a line segment. When a graph has \(K_5\) or \(K_{3,3}\) as subgraph then the graph is not planar.
 The main characteristics are:
This implementation use the BoyerMyrvold Planarity Testing.
It will return a boolean value depending upon the planarity of the graph.
Applicable only for undirected graphs.
The algorithm does not considers traversal costs in the calculations.
Running time: \(O(V)\)
Signatures¶
Summary
pgr_isPlanar(Edges SQL)  Experimental on v3.2
RETURNS BOOLEAN
SELECT * FROM pgr_isPlanar(
'SELECT id, source, target, cost, reverse_cost
FROM edge_table'
);
pgr_isplanar

t
(1 row)
Parameters¶
Parameter 
Type 
Default 
Description 

Edges SQL 

SQL query as described below. 
Inner query¶
 Edges SQL
an SQL query, which should return a set of rows with the following columns:
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 



reverse_cost 

1 

Where:
 ANYINTEGER
SMALLINT, INTEGER, BIGINT
 ANYNUMERICAL
SMALLINT, INTEGER, BIGINT, REAL, FLOAT
Result Columns¶
Returns a boolean (pgr_isplanar)
Column 
Type 
Description 

pgr_isplanar 


Additional Example:¶
The following edges will make the subgraph with vertices {3, 4, 6, 9, 16} a \(K_5\) graph.
INSERT INTO edge_table (source, target, cost, reverse_cost) VALUES
(3, 9, 1, 1), (3, 16, 1, 1),
(4, 6, 1, 1), (4, 16, 1, 1),
(6, 16, 1, 1),
(9, 16, 1, 1);
INSERT 0 6
The new graph is not planar because it has a \(K_5\) subgraph. Edges in blue represent \(K_5\) subgraph.
SELECT * FROM pgr_isPlanar(
'SELECT id, source, target, cost, reverse_cost
FROM edge_table'
);
pgr_isplanar

f
(1 row)