pgr_chinesePostman - Experimental

pgr_chinesePostman - Calculates the shortest circuit path which contains every edge in a directed graph and starts and ends on the same vertex.

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 signature

Description

The main characteristics are:

  • Process is done only on edges with positive costs.

  • Running time: \(O(E * (E + V * logV))\)

  • Graph must be connected.

  • Returns EMPTY SET on a disconnected graph

Signatures

pgr_chinesePostman( Edges SQL )
RETURNS SET OF (seq, node, edge, cost, agg_cost)
OR EMPTY SET
Example : 

SELECT * FROM pgr_chinesePostman(
  'SELECT id, source, target, cost, reverse_cost
  FROM edges WHERE id < 17');
 seq  node  edge  cost  agg_cost
-----+------+------+------+----------
   1     1     6     1         0
   2     3     7     1         1
   3     7     4     1         2
   4     6     4     1         3
   5     7     8     1         4
   6    11     8     1         5
   7     7    10     1         6
   8     8    12     1         7
   9    12    13     1         8
  10    17    15     1         9
  11    16    15     1        10
  12    17    15     1        11
  13    16    16     1        12
  14    15    16     1        13
  15    16     9     1        14
  16    11    11     1        15
  17    12    13     1        16
  18    17    15     1        17
  19    16    16     1        18
  20    15     3     1        19
  21    10     5     1        20
  22    11     9     1        21
  23    16    16     1        22
  24    15     3     1        23
  25    10     2     1        24
  26     6     1     1        25
  27     5     1     1        26
  28     6     4     1        27
  29     7    10     1        28
  30     8    14     1        29
  31     9    14     1        30
  32     8    10     1        31
  33     7     7     1        32
  34     3     6     1        33
  35     1    -1     0        34
(35 rows)

Parameters

Parameter

Type

Description

Edges SQL

TEXT

Edges SQL as described below.

Inner Queries

Edges SQL

An Edges SQL that represents a directed graph 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 )

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, node, edge, cost, agg_cost)

Column

Type

Description

seq

INT

Sequential value starting from 1

node

BIGINT

Identifier of the node in the path from start_vid to end_vid .

edge

BIGINT

Identifier of the edge used to go from node to the next node in the path sequence. -1 for the last node of the path.

cost

FLOAT

Cost to traverse from node using edge to the next node in the path sequence.

agg_cost

FLOAT

Aggregate cost from start_v to node .

See Also

Indices and tables