# pgr_bridges¶

pgr_bridges - Return the bridges of an undirected graph.

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.