pgr_withPointsDD - Proposed¶

Name¶

pgr_withPointsDD - Returns the driving distance from a starting point.

Warning

These are 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.

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