# pgRouting Manual (3.6)

## pgr_chinesePostman - Experimental

- Supported versions

# `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

- Chinese Postman Problem - Family of functions (Experimental)

- Sample Data

Indices and tables

- Index

- Search Page