pgr_bdDijkstraCost - Proposed

pgr_bdDijkstraCost — Returns the shortest path(s)’s cost using Bidirectional Dijkstra algorithm.

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Boost Graph Inside

Availability: 2.5.0

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

Signature Summary

pgr_dijkstraCost(edges_sql, start_vid,  end_vid)
pgr_bdDijkstraCost(edges_sql, start_vid, end_vid, directed)
pgr_bdDijkstraCost(edges_sql, start_vid, end_vids, directed)
pgr_bdDijkstraCost(edges_sql, start_vids, end_vid, directed)
pgr_bdDijkstraCost(edges_sql, start_vids, end_vids, directed)

RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET

Signatures

Minimal signature

pgr_bdDijkstraCost(edges_sql, start_vid, end_vid)
RETURNS SET OF (seq, path_seq, node, edge, cost, agg_cost) or EMPTY SET

The minimal signature is for a directed graph from one start_vid to one end_vid:

Example: 
SELECT * FROM pgr_bdDijkstraCost(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    2, 3
);
 start_vid | end_vid | agg_cost 
-----------+---------+----------
         2 |       3 |        5
(1 row)

pgr_bdDijkstraCost One to One

pgr_bdDijkstraCost(edges_sql, start_vid, end_vid, directed)
RETURNS SET OF (seq, path_seq, node, edge, cost, agg_cost) or EMPTY SET
This signature finds the shortest path from one start_vid to one end_vid:
  • on a directed graph when directed flag is missing or is set to true.
  • on an undirected graph when directed flag is set to false.
Example: 
SELECT * FROM pgr_bdDijkstra(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    2, 3,
    false
);
 seq | path_seq | node | edge | cost | agg_cost 
-----+----------+------+------+------+----------
   1 |        1 |    2 |    2 |    1 |        0
   2 |        2 |    3 |   -1 |    0 |        1
(2 rows)

pgr_bdDijkstraCost One to many

pgr_bdDijkstra(edges_sql, start_vid, end_vids, directed)
RETURNS SET OF (seq, path_seq, end_vid, node, edge, cost, agg_cost) or EMPTY SET
This signature finds the shortest path from one start_vid to each end_vid in end_vids:
  • on a directed graph when directed flag is missing or is set to true.
  • on an undirected graph when directed flag is set to false.

Using this signature, will load once the graph and perform a one to one pgr_dijkstra where the starting vertex is fixed, and stop when all end_vids are reached.

  • The result is equivalent to the union of the results of the one to one pgr_dijkstra.
  • The extra end_vid in the result is used to distinguish to which path it belongs.
Example: 
SELECT * FROM pgr_bdDijkstraCost(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    2, ARRAY[3, 11]);
 start_vid | end_vid | agg_cost 
-----------+---------+----------
         2 |       3 |        5
         2 |      11 |        3
(2 rows)

pgr_bdDijkstraCost Many to One

pgr_bdDijkstra(edges_sql, start_vids, end_vid, directed)
RETURNS SET OF (seq, path_seq, start_vid, node, edge, cost, agg_cost) or EMPTY SET
This signature finds the shortest path from each start_vid in start_vids to one end_vid:
  • on a directed graph when directed flag is missing or is set to true.
  • on an undirected graph when directed flag is set to false.

Using this signature, will load once the graph and perform several one to one pgr_dijkstra where the ending vertex is fixed.

  • The result is the union of the results of the one to one pgr_dijkstra.
  • The extra start_vid in the result is used to distinguish to which path it belongs.
Example: 
SELECT * FROM pgr_bdDijkstra(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    ARRAY[2, 7], 3);
 seq | path_seq | start_vid | node | edge | cost | agg_cost 
-----+----------+-----------+------+------+------+----------
   1 |        1 |         2 |    2 |    4 |    1 |        0
   2 |        2 |         2 |    5 |    8 |    1 |        1
   3 |        3 |         2 |    6 |    9 |    1 |        2
   4 |        4 |         2 |    9 |   16 |    1 |        3
   5 |        5 |         2 |    4 |    3 |    1 |        4
   6 |        6 |         2 |    3 |   -1 |    0 |        5
   7 |        1 |         7 |    7 |    6 |    1 |        0
   8 |        2 |         7 |    8 |    7 |    1 |        1
   9 |        3 |         7 |    5 |    8 |    1 |        2
  10 |        4 |         7 |    6 |    9 |    1 |        3
  11 |        5 |         7 |    9 |   16 |    1 |        4
  12 |        6 |         7 |    4 |    3 |    1 |        5
  13 |        7 |         7 |    3 |   -1 |    0 |        6
(13 rows)

pgr_bdDijkstraCost Many to Many

pgr_bdDijkstra(edges_sql, start_vids, end_vids, directed)
RETURNS SET OF (seq, path_seq, start_vid, end_vid, node, edge, cost, agg_cost) or EMPTY SET
This signature finds the shortest path from each start_vid in start_vids to each end_vid in end_vids:
  • on a directed graph when directed flag is missing or is set to true.
  • on an undirected graph when directed flag is set to false.

Using this signature, will load once the graph and perform several one to Many pgr_dijkstra for all start_vids.

  • The result is the union of the results of the one to one pgr_dijkstra.
  • The extra start_vid in the result is used to distinguish to which path it belongs.

The extra start_vid and end_vid in the result is used to distinguish to which path it belongs.

Example: 
SELECT * FROM pgr_bdDijkstra(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    ARRAY[2, 7], ARRAY[3, 11]);
 seq | path_seq | start_vid | end_vid | node | edge | cost | agg_cost 
-----+----------+-----------+---------+------+------+------+----------
   1 |        1 |         2 |       3 |    2 |    4 |    1 |        0
   2 |        2 |         2 |       3 |    5 |    8 |    1 |        1
   3 |        3 |         2 |       3 |    6 |    9 |    1 |        2
   4 |        4 |         2 |       3 |    9 |   16 |    1 |        3
   5 |        5 |         2 |       3 |    4 |    3 |    1 |        4
   6 |        6 |         2 |       3 |    3 |   -1 |    0 |        5
   7 |        1 |         2 |      11 |    2 |    4 |    1 |        0
   8 |        2 |         2 |      11 |    5 |    8 |    1 |        1
   9 |        3 |         2 |      11 |    6 |   11 |    1 |        2
  10 |        4 |         2 |      11 |   11 |   -1 |    0 |        3
  11 |        1 |         7 |       3 |    7 |    6 |    1 |        0
  12 |        2 |         7 |       3 |    8 |    7 |    1 |        1
  13 |        3 |         7 |       3 |    5 |    8 |    1 |        2
  14 |        4 |         7 |       3 |    6 |    9 |    1 |        3
  15 |        5 |         7 |       3 |    9 |   16 |    1 |        4
  16 |        6 |         7 |       3 |    4 |    3 |    1 |        5
  17 |        7 |         7 |       3 |    3 |   -1 |    0 |        6
  18 |        1 |         7 |      11 |    7 |    6 |    1 |        0
  19 |        2 |         7 |      11 |    8 |    7 |    1 |        1
  20 |        3 |         7 |      11 |    5 |   10 |    1 |        2
  21 |        4 |         7 |      11 |   10 |   12 |    1 |        3
  22 |        5 |         7 |      11 |   11 |   -1 |    0 |        4
(22 rows)

Description of the Signatures

Description of the edges_sql query for dijkstra like functions

edges_sql:an SQL query, which should return a set of rows 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

Description of the parameters of the signatures

Column Type Default Description
sql TEXT   SQL query as described above.
start_vid BIGINT   Identifier of the starting vertex of the path.
start_vids ARRAY[BIGINT]   Array of identifiers of starting vertices.
end_vid BIGINT   Identifier of the ending vertex of the path.
end_vids ARRAY[BIGINT]   Array of identifiers of ending vertices.
directed BOOLEAN true
  • When true Graph is considered Directed
  • When false the graph is considered as Undirected.

Description of the return values for a Cost function

Returns set of (start_vid, end_vid, agg_cost)

Column Type Description
start_vid BIGINT Identifier of the starting vertex. Used when multiple starting vetrices are in the query.
end_vid BIGINT Identifier of the ending vertex. Used when multiple ending vertices are in the query.
agg_cost FLOAT Aggregate cost from start_vid to end_vid.