pgr_articulationPoints¶

pgr_articulationPoints - Return the articulation points of an undirected graph.

_images/boost-inside.jpeg — Boost Graph Inside¶

Availability

Version 3.0.0
- Return columns change: seq is removed
- Official function
Version 2.5.0
- New experimental function

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:

The signature is for an undirected graph.
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 edge_table'
);
 node
------
    2
    5
    8
   10
(4 rows)

Parameters¶

Parameter	Type	Default	Description
Edges SQL	`TEXT`		Inner query as described below.

Inner query¶

edges SQL: an SQL query of an undirected graph, which should return a set of rows with the following columns:

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