pgr_transitiveClosure - Experimental

pgr_transitiveClosure — Transitive closure graph of a directed graph.

_images/boost-inside.jpeg

Boost Graph Inside

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 ANY-INTEGER and ANY-NUMERICAL

    • 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 3.0.0

    • New experimental function

Description

Transforms the input directed graph into the transitive closure of the graph.

The main characteristics are:

  • Process is valid for directed graphs.

    • The transitive closure of an undirected graph produces a cluster graph

    • Reachability between vertices on an undirected graph happens when they belong to the same connected component. (see pgr_connectedComponents)

  • The returned values are not ordered

  • The returned graph is compresed

  • Running time: \(O(|V||E|)\)

Signatures

Summary

The pgr_transitiveClosure function has the following signature:

pgr_transitiveClosure(Edges SQL)
Returns set of (seq, vid, target_array)
Example:

Rechability of a subgraph

SELECT * FROM pgr_transitiveclosure(
  'SELECT id, source, target, cost, reverse_cost
  FROM edges WHERE id IN (2, 3, 5, 11, 12, 13, 15)')
ORDER BY vid;
 seq | vid |    target_array
-----+-----+--------------------
   1 |   6 | {}
   6 |   8 | {12,17,16}
   2 |  10 | {12,17,16,11,6}
   4 |  11 | {12,17,16}
   5 |  12 | {17,16}
   3 |  15 | {12,17,16,10,11,6}
   8 |  16 | {17,16}
   7 |  17 | {17,16}
(8 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 (seq, vid, target_array)

Column

Type

Description

seq

INTEGER

Sequential value starting from \(1\)

vid

BIGINT

Identifier of the source of the edges

target_array

BIGINT

Identifiers of the targets of the edges

  • Identifiers of the vertices that are reachable from vertex v.

See Also

Indices and tables