pgr_maxCardinalityMatch

pgr_maxCardinalityMatch — Calculates a maximum cardinality matching in a graph.

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Availability

  • Version 3.0.0

    • Official function

  • Version 2.5.0

    • Renamed from pgr_maximumCardinalityMatching

    • Proposed function

  • Version 2.3.0

    • New Experimental function

Support

Description

The main characteristics are:

  • A matching or independent edge set in a graph is a set of edges without common vertices.

  • A maximum matching is a matching that contains the largest possible number of edges.

    • There may be many maximum matchings.

    • Calculates one possible maximum cardinality matching in a graph.

  • The graph can be directed or undirected.

  • Running time: \(O( E*V * \alpha(E,V))\)

Signatures

pgr_maxCardinalityMatch(Edges SQL [, directed])

RETURNS SET OF (seq, edge_id, source, target)
OR EMPTY SET
Example

For an undirected graph

SELECT * FROM pgr_maxCardinalityMatch(
    'SELECT id, source, target, cost AS going, reverse_cost AS coming FROM edge_table',
    directed := false
);
 seq | edge | source | target
-----+------+--------+--------
   1 |    1 |      1 |      2
   2 |    3 |      3 |      4
   3 |    9 |      6 |      9
   4 |    6 |      7 |      8
   5 |   14 |     10 |     13
   6 |   13 |     11 |     12
   7 |   17 |     14 |     15
   8 |   18 |     16 |     17
(8 rows)

Parameters

Parameter

Type

Default

Description

edges_sql

TEXT

SQL query as described above.

directed

BOOLEAN

true

Determines the type of the graph. - When true Graph is considered Directed - When false the graph is considered as Undirected.

Inner query

Edges SQL

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

Column

Type

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.

going

ANY-NUMERIC

A positive value represents the existence of the edge (source, target).

coming

ANY-NUMERIC

A positive value represents the existence of the edge (target, source).

Where:

ANY-INTEGER

SMALLINT, INTEGER, BIGINT

ANY-NUMERIC

SMALLINT, INTEGER, BIGINT, REAL FLOAT

Result Columns

Column

Type

Description

seq

INT

Sequential value starting from 1.

edge

BIGINT

Identifier of the edge in the original query.

source

BIGINT

Identifier of the first end point of the edge.

target

BIGINT

Identifier of the second end point of the edge.