pgr_primDFS¶
pgr_primDFS
— Prim algorithm for Minimum Spanning Tree with Depth First
Search ordering.

Boost Graph Inside¶
Availability
Version 3.0.0
New Official function
Support
Supported versions: current(3.0)
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¶
pgr_primDFS(Edges SQL, Root vid [, max_depth])
pgr_primDFS(Edges SQL, Root vids [, max_depth])
RETURNS SET OF (seq, depth, start_vid, node, edge, cost, agg_cost)
Single vertex¶
pgr_primDFS(Edges SQL, Root vid [, max_depth])
RETURNS SET OF (seq, depth, start_vid, node, edge, cost, agg_cost)
- Example
The Minimum Spanning Tree having as root vertex \(2\)
SELECT * FROM pgr_primDFS(
'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
2
);
seq | depth | start_vid | node | edge | cost | agg_cost
-----+-------+-----------+------+------+------+----------
1 | 0 | 2 | 2 | -1 | 0 | 0
2 | 1 | 2 | 1 | 1 | 1 | 1
3 | 1 | 2 | 3 | 2 | 1 | 1
4 | 2 | 2 | 4 | 3 | 1 | 2
5 | 2 | 2 | 6 | 5 | 1 | 2
6 | 3 | 2 | 9 | 9 | 1 | 3
7 | 3 | 2 | 11 | 11 | 1 | 3
8 | 4 | 2 | 12 | 13 | 1 | 4
9 | 1 | 2 | 5 | 4 | 1 | 1
10 | 2 | 2 | 8 | 7 | 1 | 2
11 | 3 | 2 | 7 | 6 | 1 | 3
12 | 2 | 2 | 10 | 10 | 1 | 2
13 | 3 | 2 | 13 | 14 | 1 | 3
(13 rows)
Multiple vertices¶
pgr_primDFS(Edges SQL, Root vids [, max_depth])
RETURNS SET OF (seq, depth, start_vid, node, edge, cost, agg_cost)
- Example
The Minimum Spanning Tree starting on vertices \(\{13, 2\}\) with \(depth <= 3\)
SELECT * FROM pgr_primDFS(
'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
ARRAY[13,2], max_depth := 3
);
seq | depth | start_vid | node | edge | cost | agg_cost
-----+-------+-----------+------+------+------+----------
1 | 0 | 2 | 2 | -1 | 0 | 0
2 | 1 | 2 | 1 | 1 | 1 | 1
3 | 1 | 2 | 3 | 2 | 1 | 1
4 | 2 | 2 | 4 | 3 | 1 | 2
5 | 2 | 2 | 6 | 5 | 1 | 2
6 | 3 | 2 | 9 | 9 | 1 | 3
7 | 3 | 2 | 11 | 11 | 1 | 3
8 | 1 | 2 | 5 | 4 | 1 | 1
9 | 2 | 2 | 8 | 7 | 1 | 2
10 | 3 | 2 | 7 | 6 | 1 | 3
11 | 2 | 2 | 10 | 10 | 1 | 2
12 | 3 | 2 | 13 | 14 | 1 | 3
13 | 0 | 13 | 13 | -1 | 0 | 0
14 | 1 | 13 | 10 | 14 | 1 | 1
15 | 2 | 13 | 5 | 10 | 1 | 2
16 | 3 | 13 | 2 | 4 | 1 | 3
17 | 3 | 13 | 8 | 7 | 1 | 3
(17 rows)
Parameters¶
Parameter |
Type |
Description |
---|---|---|
Edges SQL |
|
SQL query described in Inner query. |
Root vid |
|
Identifier of the root vertex of the tree.
|
Root vids |
|
Array of identifiers of the root vertices.
|
Optional Parameters¶
Parameter |
Type |
Default |
Description |
---|---|---|---|
max_depth |
|
\(9223372036854775807\) |
Upper limit for depth of node in the tree
|
Inner query¶
Column |
Type |
Default |
Description |
---|---|---|---|
id |
|
Identifier of the edge. |
|
source |
|
Identifier of the first end point vertex of the edge. |
|
target |
|
Identifier of the second end point vertex of the edge. |
|
cost |
|
Weight of the edge (source, target)
|
|
reverse_cost |
|
-1 |
Weight of the edge (target, source),
|
Where:
- ANY-INTEGER
SMALLINT, INTEGER, BIGINT
- ANY-NUMERICAL
SMALLINT, INTEGER, BIGINT, REAL, FLOAT
Result Columns¶
Returns SET OF (seq, depth, start_vid, node, edge, cost, agg_cost)
Column |
Type |
Description |
---|---|---|
seq |
|
Sequential value starting from \(1\). |
depth |
|
Depth of the
|
start_vid |
|
Identifier of the root vertex.
|
node |
|
Identifier of |
edge |
|
Identifier of the
|
cost |
|
Cost to traverse |
agg_cost |
|
Aggregate cost from |