pgr_bridges

pgr_bridges - Return the bridges 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

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)
images/bridge_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 (edge)

Column

Type

Description

edge

BIGINT

Identifier of the edge that is a bridge.

See Also

Indices and tables