pgr_articulationPoints¶
pgr_articulationPoints
- Return the articulation points of an undirected graph.
Availability
- Version 3.0.0
- Return columns change:
seq
is removed - Official function
- Return columns change:
- 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)
|
|
reverse_cost | ANY-NUMERICAL |
-1 | Weight of the edge (target, source),
|
Where:
ANY-INTEGER: | SMALLINT, INTEGER, BIGINT |
---|---|
ANY-NUMERICAL: | SMALLINT, INTEGER, BIGINT, REAL, FLOAT |
See Also¶
- Components - Family of functions
- The queries use the Sample Data network.
- Boost: Biconnected components & articulation points
- wikipedia: Biconnected component
Indices and tables