pgr_withPointsDD - Proposed

Name

pgr_withPointsDD - Returns the driving distance from a starting point.

Warning

Proposed functions for next mayor release.

  • They are not officially in the current release.
  • They will likely officially be part of the next mayor release:
    • The functions make use of ANY-INTEGER and ANY-NUMERICAL
    • Name might not change. (But still can)
    • Signature might not change. (But still can)
    • Functionality might not change. (But still can)
    • pgTap tests have being done. But might need more.
    • Documentation might need refinement.
_images/boost-inside.jpeg

Boost Graph Inside

Availability: 2.2.0

Synopsis

Modify the graph to include points and using Dijkstra algorithm, extracts all the nodes and points that have costs less than or equal to the value distance from the starting point. The edges extracted will conform the corresponding spanning tree.

Signature Summary

pgr_withPointsDD(edges_sql, points_sql, start_vid, distance)
pgr_withPointsDD(edges_sql, points_sql, start_vid, distance, directed, driving_side, details)
pgr_withPointsDD(edges_sql, points_sql, start_vids, distance, directed, driving_side, details, equicost)
RETURNS SET OF (seq, node, edge, cost, agg_cost)

Signatures

Minimal Use

The minimal signature:
  • Is for a directed graph.
  • The driving side is set as b both. So arriving/departing to/from the point(s) can be in any direction.
  • No details are given about distance of other points of the query.
pgr_withPointsDD(edges_sql, points_sql, start_vid, distance)
    directed:=true, driving_side:='b', details:=false)
RETURNS SET OF (seq, node, edge, cost, agg_cost)
Example:
SELECT * FROM pgr_withPointsDD(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, 3.8);
 seq | node | edge | cost | agg_cost 
-----+------+------+------+----------
   1 |   -1 |   -1 |    0 |        0
   2 |    1 |    1 |  0.4 |      0.4
   3 |    2 |    1 |  0.6 |      0.6
   4 |    5 |    4 |  0.3 |      1.6
   5 |    6 |    8 |    1 |      2.6
   6 |    8 |    7 |    1 |      2.6
   7 |   10 |   10 |    1 |      2.6
   8 |    7 |    6 |  0.3 |      3.6
   9 |    9 |    9 |    1 |      3.6
  10 |   11 |   11 |    1 |      3.6
  11 |   13 |   14 |    1 |      3.6
(11 rows)

Driving distance from a single point

Finds the driving distance depending on the optional parameters setup.

pgr_withPointsDD(edges_sql, points_sql, start_vids, distance,
    directed:=true, driving_side:='b', details:=false)
RETURNS SET OF (seq, node, edge, cost, agg_cost)
Example:Right side driving topology
SELECT * FROM pgr_withPointsDD(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, 3.8,
    driving_side := 'r',
    details := true);
 seq | node | edge | cost | agg_cost 
-----+------+------+------+----------
   1 |   -1 |   -1 |    0 |        0
   2 |    1 |    1 |  0.4 |      0.4
   3 |    2 |    1 |    1 |      1.4
   4 |   -6 |    4 |  0.7 |      2.1
   5 |    5 |    4 |  0.3 |      2.4
   6 |    6 |    8 |    1 |      3.4
   7 |    8 |    7 |    1 |      3.4
   8 |   10 |   10 |    1 |      3.4
(8 rows)

Driving distance from many starting points

Finds the driving distance depending on the optional parameters setup.

pgr_withPointsDD(edges_sql, points_sql, start_vids, distance,
    directed:=true, driving_side:='b', details:=false, equicost:=false)
RETURNS SET OF (seq, node, edge, cost, agg_cost)

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 Points SQL query

points_sql:an SQL query, which should return a set of rows with the following columns:
Column Type Description
pid ANY-INTEGER

(optional) Identifier of the point.

  • If column present, it can not be NULL.
  • If column not present, a sequential identifier will be given automatically.
edge_id ANY-INTEGER Identifier of the “closest” edge to the point.
fraction ANY-NUMERICAL Value in <0,1> that indicates the relative postition from the first end point of the edge.
side CHAR

(optional) Value in [‘b’, ‘r’, ‘l’, NULL] indicating if the point is:

  • In the right, left of the edge or
  • If it doesn’t matter with ‘b’ or NULL.
  • If column not present ‘b’ is considered.

Where:

ANY-INTEGER:smallint, int, bigint
ANY-NUMERICAL:smallint, int, bigint, real, float

Description of the parameters of the signatures

Parameter Type Description
edges_sql TEXT Edges SQL query as described above.
points_sql TEXT Points SQL query as described above.
start_vid ANY-INTEGER Starting point id
distance ANY-NUMERICAL Distance from the start_pid
directed BOOLEAN (optional). When false the graph is considered as Undirected. Default is true which considers the graph as Directed.
driving_side CHAR
(optional). Value in [‘b’, ‘r’, ‘l’, NULL] indicating if the driving side is:
  • In the right or left or
  • If it doesn’t matter with ‘b’ or NULL.
  • If column not present ‘b’ is considered.
details BOOLEAN (optional). When true the results will include the driving distance to the points with in the distance. Default is false which ignores other points of the points_sql.
equicost BOOLEAN (optional). When true the nodes will only appear in the closest start_v list. Default is false which resembles several calls using the single starting point signatures. Tie brakes are arbitrary.

Description of the return values

Returns set of (seq, node, edge, cost, agg_cost)

Column Type Description
seq INT row sequence.
node BIGINT Identifier of the node within the Distance from start_pid. If details =: true a negative value is the identifier of a point.
edge BIGINT
Identifier of the edge used to go from node to the next node in the path sequence.
  • -1 when start_vid = node.
cost FLOAT
Cost to traverse edge.
  • 0 when start_vid = node.
agg_cost FLOAT
Aggregate cost from start_vid to node.
  • 0 when start_vid = node.

Examples for queries marked as directed with cost and reverse_cost columns

The examples in this section use the following Graph 1: Directed, with cost and reverse cost

Example:Left side driving topology
SELECT * FROM pgr_withPointsDD(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, 3.8,
    driving_side := 'l',
    details := true);
 seq | node | edge | cost | agg_cost 
-----+------+------+------+----------
   1 |   -1 |   -1 |    0 |        0
   2 |    2 |    1 |  0.6 |      0.6
   3 |   -6 |    4 |  0.7 |      1.3
   4 |    5 |    4 |  0.3 |      1.6
   5 |    1 |    1 |    1 |      1.6
   6 |    6 |    8 |    1 |      2.6
   7 |    8 |    7 |    1 |      2.6
   8 |   10 |   10 |    1 |      2.6
   9 |   -3 |   12 |  0.6 |      3.2
  10 |   -4 |    6 |  0.7 |      3.3
  11 |    7 |    6 |  0.3 |      3.6
  12 |    9 |    9 |    1 |      3.6
  13 |   11 |   11 |    1 |      3.6
  14 |   13 |   14 |    1 |      3.6
(14 rows)

Example:Does not matter driving side.
SELECT * FROM pgr_withPointsDD(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table ORDER BY id',
    'SELECT pid, edge_id, fraction, side from pointsOfInterest',
    -1, 3.8,
    driving_side := 'b',
    details := true);
 seq | node | edge | cost | agg_cost 
-----+------+------+------+----------
   1 |   -1 |   -1 |    0 |        0
   2 |    1 |    1 |  0.4 |      0.4
   3 |    2 |    1 |  0.6 |      0.6
   4 |   -6 |    4 |  0.7 |      1.3
   5 |    5 |    4 |  0.3 |      1.6
   6 |    6 |    8 |    1 |      2.6
   7 |    8 |    7 |    1 |      2.6
   8 |   10 |   10 |    1 |      2.6
   9 |   -3 |   12 |  0.6 |      3.2
  10 |   -4 |    6 |  0.7 |      3.3
  11 |    7 |    6 |  0.3 |      3.6
  12 |    9 |    9 |    1 |      3.6
  13 |   11 |   11 |    1 |      3.6
  14 |   13 |   14 |    1 |      3.6
(14 rows)

The queries use the Sample Data network.

History

  • Proposed in version 2.2

See Also

Indices and tables