pgr_primDFS - pgRouting Manual (3.4)

Description

Visits and extracts the nodes information in Depth First Search ordering of the Minimum Spanning Tree created using Prims’s algorithm.

The main Characteristics are:

• It’s implementation is only on undirected graph.

• Process is done only on edges with positive costs.

• When the graph is connected

  • The resulting edges make up a tree

• When the graph is not connected,

  • Finds a minimum spanning tree for each connected component.

  • The resulting edges make up a forest.

• Prim’s running time: \(O(E * log V)\)

• Returned tree nodes from a root vertex are on Depth First Search order

• Depth First Search Running time: \(O(E + V)\)

Signatures

SELECT * FROM pgr_primDFS(
  'SELECT id, source, target, cost, reverse_cost FROM edges ORDER BY id',
  6);
 seq  depth  start_vid  node  edge  cost  agg_cost
-----+-------+-----------+------+------+------+----------
   1      0          6     6    -1     0         0
   2      1          6     5     1     1         1
   3      1          6    10     2     1         1
   4      2          6    15     3     1         2
   5      2          6    11     5     1         2
   6      3          6    16     9     1         3
   7      3          6    12    11     1         3
   8      4          6    17    13     1         4
   9      1          6     7     4     1         1
  10      2          6     3     7     1         2
  11      3          6     1     6     1         3
  12      2          6     8    10     1         2
  13      3          6     9    14     1         3
(13 rows)

SELECT * FROM pgr_primDFS(
  'SELECT id, source, target, cost, reverse_cost FROM edges ORDER BY id',
  ARRAY[9, 6], max_depth => 3);
 seq  depth  start_vid  node  edge  cost  agg_cost
-----+-------+-----------+------+------+------+----------
   1      0          6     6    -1     0         0
   2      1          6     5     1     1         1
   3      1          6    10     2     1         1
   4      2          6    15     3     1         2
   5      2          6    11     5     1         2
   6      3          6    16     9     1         3
   7      3          6    12    11     1         3
   8      1          6     7     4     1         1
   9      2          6     3     7     1         2
  10      3          6     1     6     1         3
  11      2          6     8    10     1         2
  12      3          6     9    14     1         3
  13      0          9     9    -1     0         0
  14      1          9     8    14     1         1
  15      2          9     7    10     1         2
  16      3          9     6     4     1         3
  17      3          9     3     7     1         3
(17 rows)

Parameters

Where:

ANY-INTEGER :

SMALLINT, INTEGER, BIGINT

ANY-NUMERIC :

SMALLINT, INTEGER, BIGINT, REAL, FLOAT, NUMERIC

Inner Queries

Result Columns

Returns SET OF (seq, depth, start_vid, node, edge, cost, agg_cost)

Where:

ANY-INTEGER :

SMALLINT, INTEGER, BIGINT

ANY-NUMERIC :

SMALLINT, INTEGER, BIGINT, REAL, FLOAT, NUMERIC

See Also

• Spanning Tree - Category

• Prim - Family of functions

• Sample Data

• Boost: Prim’s algorithm documentation

• Wikipedia: Prim’s algorithm

Indices and tables

• Index

• Search Page