# pgRouting Manual (3.6)

## pgr_bridges

# `pgr_bridges`

`pgr_bridges` - Return the bridges of an undirected graph.

Boost Graph Inside

Availability

- Version 3.0.0

  - Result 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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