pgr_articulationPoints

pgr_articulationPoints - Return the articulation points of an undirected graph.

_images/boost-inside.jpeg

Boost Graph Inside

Availability

Description

Those vertices that belong to more than one biconnected component are called articulation points or, equivalently, cut vertices. Articulation points are vertices whose removal would increase the number of connected components in the graph. This implementation can only be used with an undirected graph.

The main characteristics are:

  • Works for undirected graphs.
  • The returned values are ordered:
    • node ascending
  • Running time: \(O(V + E)\)

Signatures

pgr_articulationPoints(Edges SQL)
RETURNS SET OF (node)
OR EMPTY SET
Example:The articulation points of the graph
SELECT * FROM pgr_articulationPoints(
  'SELECT id, source, target, cost, reverse_cost FROM edges'
);
 node
------
    3
    6
    7
    8
(4 rows)

Nodes in red are the articulation points.

_images/ap_sampledata.png

Parameters

Parameter Type Description
Edges SQL TEXT Edges SQL as described below.

Inner Queries

Edges SQL

Column Type Default Description
id ANY-INTEGER   Identifier of the edge.
source ANY-INTEGER   Identifier of the first end point vertex of the edge.
target ANY-INTEGER   Identifier of the second end point vertex of the edge.
cost ANY-NUMERICAL   Weight of the edge (source, target)
reverse_cost ANY-NUMERICAL -1

Weight of the edge (target, source)

  • When negative: edge (target, source) does not exist, therefore it’s not part of the graph.

Where:

ANY-INTEGER:SMALLINT, INTEGER, BIGINT
ANY-NUMERICAL:SMALLINT, INTEGER, BIGINT, REAL, FLOAT

Result Columns

Returns set of (node)

Column Type Description
node BIGINT Identifier of the vertex.