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 function

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

Parameters

Column

Type

Default

Description

edges_sql

TEXT

The edges SQL query as described in Inner query .

Inner query

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)

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

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