# pgRouting Manual (3.0-rc1)

## 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

Support

- Supported versions current(3.0)

## 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 |    4 |    3 |    1 |        0
       2 |    3 |    2 |    1 |        1
       3 |    2 |    1 |    1 |        2
       4 |    1 |    1 |    1 |        3
       5 |    2 |    4 |    1 |        4
       6 |    5 |    4 |    1 |        5
       7 |    2 |    4 |    1 |        6
       8 |    5 |    7 |    1 |        7
       9 |    8 |    6 |    1 |        8
      10 |    7 |    6 |    1 |        9
      11 |    8 |    7 |    1 |       10
      12 |    5 |    8 |    1 |       11
      13 |    6 |    8 |    1 |       12
      14 |    5 |   10 |    1 |       13
      15 |   10 |   10 |    1 |       14
      16 |    5 |   10 |    1 |       15
      17 |   10 |   14 |    1 |       16
      18 |   13 |   14 |    1 |       17
      19 |   10 |   12 |    1 |       18
      20 |   11 |   13 |    1 |       19
      21 |   12 |   15 |    1 |       20
      22 |    9 |    9 |    1 |       21
      23 |    6 |    9 |    1 |       22
      24 |    9 |   15 |    1 |       23
      25 |   12 |   15 |    1 |       24
      26 |    9 |   16 |    1 |       25
      27 |    4 |   16 |    1 |       26
      28 |    9 |   16 |    1 |       27
      29 |    4 |    3 |    1 |       28
      30 |    3 |    5 |    1 |       29
      31 |    6 |   11 |    1 |       30
      32 |   11 |   13 |    1 |       31
      33 |   12 |   15 |    1 |       32
      34 |    9 |   16 |    1 |       33
      35 |    4 |   -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

- Chinese Postman Problem - Family of functions (Experimental)

Indices and tables

- Index
- Search Page