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:

The signature is for an undirected graph.
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 edge_table'
);
 edge
------
    1
    6
    7
   14
   17
   18
(6 rows)

Parameters¶

Parameter	Type	Default	Description
Edges SQL	`TEXT`		Inner query as described below.

Inner query¶

edges SQL: an SQL query of an undirected graph, which should return a set of rows with the following columns:

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) When negative: edge (source, target) does not exist, therefore it’s not part of the graph.
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.