pgr_bridges

pgr_bridges - Return the bridges of an undirected graph.

Boost Graph Inside

Availability

• Version 3.0.0

  • Return columns change: seq is removed

  • Official function

• Version 2.5.0

  • New experimental function

Description

A bridge is an edge of an undirected graph whose deletion increases its number of connected components. This implementation can only be used with an undirected graph.

The main characteristics are:

• Works for undirected graphs.

• The returned values are ordered:

  • edge ascending

• Running time: \(O(E * (V + E))\)

Signatures

pgr_bridges(Edges SQL)

RETURNS SET OF (edge)

OR EMPTY SET

Example:

The bridges of the graph

SELECT * FROM pgr_bridges(
  'SELECT id, source, target, cost, reverse_cost FROM edges'
);
 edge
------
    1
    6
    7
   14
   17
   18
(6 rows)

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 (edge)

Column	Type	Description
edge	BIGINT	Identifier of the edge that is a bridge.

See Also

• https://en.wikipedia.org/wiki/Bridge_%28graph_theory%29

• The queries use the Sample Data network.

Indices and tables

• Index

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