pgr_biconnectedComponents

pgr_biconnectedComponents — Biconnected components of an undirected graph.

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Boost Graph Inside

Availability

Description

The biconnected components of an undirected graph are the maximal subsets of vertices such that the removal of a vertex from particular component will not disconnect the component. Unlike connected components, vertices may belong to multiple biconnected components. Vertices can be present in multiple biconnected components, but each edge can only be contained in a single biconnected component.

The main characteristics are:

  • Works for undirected graphs.
  • Components are described by edges.
  • The returned values are ordered:
    • component ascending.
    • edge ascending.
  • Running time: \(O(V + E)\)

Signatures

pgr_biconnectedComponents(Edges SQL)
RETURNS SET OF (seq, component, edge)
OR EMPTY SET
Example:The biconnected components of the graph
SELECT * FROM pgr_biconnectedComponents(
  'SELECT id, source, target, cost, reverse_cost FROM edges'
);
 seq | component | edge
-----+-----------+------
   1 |         1 |    1
   2 |         2 |    2
   3 |         2 |    3
   4 |         2 |    4
   5 |         2 |    5
   6 |         2 |    8
   7 |         2 |    9
   8 |         2 |   10
   9 |         2 |   11
  10 |         2 |   12
  11 |         2 |   13
  12 |         2 |   15
  13 |         2 |   16
  14 |         6 |    6
  15 |         7 |    7
  16 |        14 |   14
  17 |        17 |   17
  18 |        18 |   18
(18 rows)

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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 (seq, component, edge)

Column Type Description
seq BIGINT Sequential value starting from 1.
component BIGINT

Component identifier.

  • Has the value of the minimum edge identifier in the component.
edge BIGINT Identifier of the edge that belongs to the component.

See Also

Indices and tables