pgr_aStarCost

pgr_aStarCost — Returns the aggregate cost shortest path using pgr_aStar algorithm.

_images/boost-inside.jpeg

Boost Graph Inside

Availability

  • Version 3.0.0

    • Official function

  • Version 2.4.0

    • New proposed function

Support

  • Supported versions: current(3.0) 2.6

  • Unsupported versions: 2.5 2.4

Description

The main characteristics are:

  • Default kind of graph is directed when

    • directed flag is missing.

    • directed flag is set to true

  • Unless specified otherwise, ordering is:

    • first by start_vid (if exists)

    • then by end_vid

  • Values are returned when there is a path

  • Let \(v\) and \(u\) be nodes on the graph:

    • If there is no path from \(v\) to \(u\):

      • no corresponding row is returned

      • agg_cost from \(v\) to \(u\) is \(\infty\)

    • There is no path when \(v = u\) therefore

      • no corresponding row is returned

      • agg_cost from v to u is \(0\)

  • Edges with negative costs are not included in the graph.

  • When (x,y) coordinates for the same vertex identifier differ:

    • A random selection of the vertex’s (x,y) coordinates is used.

  • Running time: \(O((E + V) * \log V)\)

Signatures

Summary

pgr_aStarCost(edges_sql, from_vid,  to_vid   [, directed] [, heuristic] [, factor] [, epsilon])
pgr_aStarCost(edges_sql, from_vid,  to_vids  [, directed] [, heuristic] [, factor] [, epsilon])
pgr_aStarCost(edges_sql, from_vids, to_vid   [, directed] [, heuristic] [, factor] [, epsilon])
pgr_aStarCost(edges_sql, from_vids, to_vids  [, directed] [, heuristic] [, factor] [, epsilon])

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

Optional parameters are named parameters and have a default value.

Using defaults

pgr_aStarCost(edges_sql, start_vid, end_vid)
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET
Example

From vertex \(2\) to vertex \(12\) on a directed graph

SELECT * FROM pgr_aStarCost(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    2, 12);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         2 |      12 |        4
(1 row)

One to One

pgr_aStarCost(edges_sql, from_vid,  to_vid   [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET
Example

From vertex \(2\) to vertex \(12\) on an undirected graph using heuristic \(2\)

SELECT * FROM pgr_aStarCost(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    2, 12,
    directed := false, heuristic := 2);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         2 |      12 |        4
(1 row)

One to many

pgr_aStarCost(edges_sql, from_vid,  to_vids  [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET
Example

From vertex \(2\) to vertices \(\{3, 12\}\) on a directed graph using heuristic \(2\)

SELECT * FROM pgr_aStarCost(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    2, ARRAY[3, 12], heuristic := 2);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         2 |       3 |        5
         2 |      12 |        4
(2 rows)

Many to One

pgr_aStarCost(edges_sql, from_vids, to_vid   [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET
Example

From vertices \(\{7, 2\}\) to vertex \(12\) on a directed graph using heuristic \(0\)

SELECT * FROM pgr_aStarCost(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    ARRAY[7, 2], 12, heuristic := 0);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         2 |      12 |        4
         7 |      12 |        5
(2 rows)

Many to Many

pgr_aStarCost(edges_sql, from_vids, to_vids  [, directed] [, heuristic] [, factor] [, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET
Example

From vertices \(\{7, 2\}\) to vertices \(\{3, 12\}\) on a directed graph using heuristic \(2\)

SELECT * FROM pgr_aStarCost(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    ARRAY[7, 2], ARRAY[3, 12], heuristic := 2);
 start_vid | end_vid | agg_cost
-----------+---------+----------
         2 |       3 |        5
         2 |      12 |        4
         7 |       3 |        6
         7 |      12 |        5
(4 rows)

Parameters

Parameter

Type

Description

edges_sql

TEXT

edges_sql inner query.

from_vid

ANY-INTEGER

Starting vertex identifier. Parameter in:

from_vids

ARRAY[ANY-INTEGER]

Array of starting vertices identifiers. Parameter in:

to_vid

ANY-INTEGER

Ending vertex identifier. Parameter in:

to_vids

ARRAY[ANY-INTEGER]

Array of ending vertices identifiers. Parameter in:

Optional Parameters

Parameter

Type

Default

Description

directed

BOOLEAN

true

  • When true the graph is considered as Directed.

  • When false the graph is considered as Undirected.

heuristic

INTEGER

5

Heuristic number. Current valid values 0~5. Default 5

  • 0: h(v) = 0 (Use this value to compare with pgr_dijkstra)

  • 1: h(v) abs(max(dx, dy))

  • 2: h(v) abs(min(dx, dy))

  • 3: h(v) = dx * dx + dy * dy

  • 4: h(v) = sqrt(dx * dx + dy * dy)

  • 5: h(v) = abs(dx) + abs(dy)

factor

FLOAT

1

For units manipulation. \(factor > 0\). See Factor

epsilon

FLOAT

1

For less restricted results. \(epsilon >= 1\).

Inner query

edges_sql

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.

x1

ANY-NUMERICAL

X coordinate of source vertex.

y1

ANY-NUMERICAL

Y coordinate of source vertex.

x2

ANY-NUMERICAL

X coordinate of target vertex.

y2

ANY-NUMERICAL

Y coordinate of target vertex.

Where:

ANY-INTEGER

SMALLINT, INTEGER, BIGINT

ANY-NUMERICAL

SMALLINT, INTEGER, BIGINT, REAL, FLOAT

Result Columns

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.