pgr_makeConnected  Experimental  pgRouting Manual (3.3)
pgr_makeConnected  Experimental
pgr_makeConnected
 Returns the set of edges that will make the graph connected.
Warning
Possible server crash

These functions might create a server crash
Warning
Experimental functions

They are not officially of the current release.

They likely will not be officially be part of the next release:

The functions might not make use of ANYINTEGER and ANYNUMERICAL

Name might change.

Signature might change.

Functionality might change.

pgTap tests might be missing.

Might need c/c++ coding.

May lack documentation.

Documentation if any might need to be rewritten.

Documentation examples might need to be automatically generated.

Might need a lot of feedback from the comunity.

Might depend on a proposed function of pgRouting

Might depend on a deprecated function of pgRouting

Availability

Version 3.2.0

New experimental function

Description
Adds the minimum number of edges needed to make the input graph connected. The algorithm first identifies all of the connected components in the graph, then adds edges to connect those components together in a path. For example, if a graph contains three connected components A, B, and C, make_connected will add two edges. The two edges added might consist of one connecting a vertex in A with a vertex in B and one connecting a vertex in B with a vertex in C.
 The main characteristics are:


It will give the minimum list of all edges which are needed in the graph to make the graph connected.

Applicable only for undirected graphs.

The algorithm does not considers traversal costs in the calculations.

Running time: \(O(V + E)\)

Signatures
Summary
pgr_makeConnected(Edges SQL)
RETURNS SET OF (seq, start_vid, end_vid)
OR EMPTY SET
 Example :

Query done on Sample Data network gives the list of edges that are needed in the graph to make it connected.
SELECT * FROM pgr_makeConnected(
'SELECT id, source, target, cost, reverse_cost
FROM edge_table'
);
seq start_vid end_vid
++
1 13 14
2 15 16
(2 rows)
Parameters
Parameter 
Type 
Default 
Description 

Edges SQL 

SQL query as described below. 
Inner query
 Edges SQL :

an SQL query, which should return a set of rows with the following columns:
Column 
Type 
Default 
Description 

id 

Identifier of the edge. 

source 

Identifier of the first end point vertex of the edge. 

target 

Identifier of the second end point vertex of the edge. 

cost 



reverse_cost 

1 

Where:
 ANYINTEGER :

SMALLINT, INTEGER, BIGINT
 ANYNUMERICAL :

SMALLINT, INTEGER, BIGINT, REAL, FLOAT
Result Columns
Returns set of
(seq,
start_vid,
end_vid)
Column 
Type 
Description 

seq 

Sequential value starting from 1 . 
start_vid 

Identifier of the first end point vertex of the edge. 
end_vid 

Identifier of the second end point vertex of the edge. 
See Also

The queries use the Sample Data network.
Indices and tables