pgr_lineGraph - Experimental

pgr_lineGraph - Transforms the given graph into its corresponding edge-based 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 2.5.0

    • New Experimental function

Description

Given a graph G, its line graph L(G) is a graph such that:

  • Each vertex of L(G) represents an edge of G

  • Two vertices of L(G) are adjacent if and only if their corresponding edges share a common endpoint in G.

Signatures

pgr_lineGraph( Edges SQL , [ directed ])
RETURNS SET OF (seq, source, target, cost, reverse_cost)
OR EMPTY SET
Example :

For a directed graph 

SELECT * FROM pgr_lineGraph(
  'SELECT id, source, target, cost, reverse_cost FROM edges'
);
 seq  source  target  cost  reverse_cost
-----+--------+--------+------+--------------
   1     -18      18     1             1
   2     -17      17     1             1
   3     -16      -3     1            -1
   4     -14     -10     1             1
   5     -14      12     1            -1
   6     -14      14     1             1
   7     -10      -7     1             1
   8     -10      -4     1             1
   9     -10       8     1             1
  10     -10      10     1             1
  11      -9      -8     1             1
  12      -9       9     1             1
  13      -9      11     1            -1
  14      -8      -7     1             1
  15      -8      -4     1             1
  16      -8       8     1             1
  17      -7      -6     1             1
  18      -7       7     1             1
  19      -6       6     1             1
  20      -3      -2     1            -1
  21      -3       5     1            -1
  22      -2      -1     1            -1
  23      -2       4     1            -1
  24       1      -1     1             1
  25       1       4     1             1
  26       4      -7     1             1
  27       4      -4     1             1
  28       5      -8     1            -1
  29       5       9     1            -1
  30       5      11     1            -1
  31       8      11     1            -1
  32       9     -16     1             1
  33       9      15     1             1
  34      10      12     1            -1
  35      11      13     1            -1
  36      12      13     1            -1
  37      13     -15     1            -1
  38      15     -15     1             1
  39      16     -16     1             1
  40      16      15     1             1
(40 rows)

Parameters

Parameter

Type

Description

Edges SQL

TEXT

Edges SQL as described below.

Optional parameters

Column

Type

Default

Description

directed

BOOLEAN

true

  • When true the graph is considered Directed

  • When false the graph is considered as Undirected .

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, source, target, cost, reverse_cost)

Column

Type

Description

seq

INTEGER

Sequential value starting from 1 .

  • Gives a local identifier for the edge

source

BIGINT

Identifier of the source vertex of the current edge.

  • When negative : the source is the reverse edge in the original graph.

target

BIGINT

Identifier of the target vertex of the current edge.

  • When negative : the target is the reverse edge in the original graph.

cost

FLOAT

Weight of the edge ( source , target ).

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

reverse_cost

FLOAT

Weight of the edge ( target , source ).

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

See Also

Indices and tables