pgr_extractVertices – Experimental

pgr_extractVertices — Extracts the vertices information based on the source and target.

Warning

Possible server crash

  • These functions might create a server crash

Warning

Experimental functions

  • They are not officially of the current release.
  • They likely will not be officially be part of the next release:
    • The functions might not make use of ANY-INTEGER and ANY-NUMERICAL
    • Name might change.
    • Signature might change.
    • Functionality might change.
    • pgTap tests might be missing.
    • Might need c/c++ coding.
    • May lack documentation.
    • Documentation if any might need to be rewritten.
    • Documentation examples might need to be automatically generated.
    • Might need a lot of feedback from the comunity.
    • Might depend on a proposed function of pgRouting
    • Might depend on a deprecated function of pgRouting

Availability

  • Version 3.0.0
    • New experimental function

Support

  • Supported versions: current(3.0)

Description

This is an auxiliary function for extracting the vertex information of the set of edges of a graph.

  • When the edge identifier is given, then it will also calculate the in and out edges

Signatures

pgr_extractVertices(Edges SQL [, dryrun])
RETURNS SETOF (id, in_edges, out_edges, x, y, geom)
Example:Extracting the vertex information
SELECT  * FROM pgr_extractVertices(
    'SELECT id, the_geom AS geom
    FROM edge_table');
 id | in_edges | out_edges |       x        |  y  |                    geom
----+----------+-----------+----------------+-----+--------------------------------------------
  1 |          | {6}       |              0 |   2 | 010100000000000000000000000000000000000040
  2 |          | {17}      |            0.5 | 3.5 | 0101000000000000000000E03F0000000000000C40
  3 | {6}      | {7}       |              1 |   2 | 0101000000000000000000F03F0000000000000040
  4 | {17}     |           | 1.999999999999 | 3.5 | 010100000068EEFFFFFFFFFF3F0000000000000C40
  5 |          | {1}       |              2 |   0 | 010100000000000000000000400000000000000000
  6 | {1}      | {2,4}     |              2 |   1 | 01010000000000000000000040000000000000F03F
  7 | {4,7}    | {8,10}    |              2 |   2 | 010100000000000000000000400000000000000040
  8 | {10}     | {12,14}   |              2 |   3 | 010100000000000000000000400000000000000840
  9 | {14}     |           |              2 |   4 | 010100000000000000000000400000000000001040
 10 | {2}      | {3,5}     |              3 |   1 | 01010000000000000000000840000000000000F03F
 11 | {5,8}    | {9,11}    |              3 |   2 | 010100000000000000000008400000000000000040
 12 | {11,12}  | {13}      |              3 |   3 | 010100000000000000000008400000000000000840
 13 |          | {18}      |            3.5 | 2.3 | 01010000000000000000000C406666666666660240
 14 | {18}     |           |            3.5 |   4 | 01010000000000000000000C400000000000001040
 15 | {3}      | {16}      |              4 |   1 | 01010000000000000000001040000000000000F03F
 16 | {9,16}   | {15}      |              4 |   2 | 010100000000000000000010400000000000000040
 17 | {13,15}  |           |              4 |   3 | 010100000000000000000010400000000000000840
(17 rows)

Parameters

Parameter Type Description
Edges SQL TEXT The set of edges of the graph. It is an Inner Query as described below.
dryrun TEXT Don’t process and get in a NOTICE the resulting query.

Inner Query

When line geometry is known

Column Type Description
id BIGINT (Optional) identifier of the edge.
geom LINESTRING LINESTRING geometry of the edge.

This inner query takes precedence over the next two inner query, therefore other columns are ignored when geom column appears.

  • Ignored columns:
    • startpoint
    • endpoint
    • source
    • target

When vertex geometry is known

To use this inner query the column geom should not be part of the set of columns.

Column Type Description
id BIGINT (Optional) identifier of the edge.
startpoint POINT POINT geometry of the starting vertex.
endpoint POINT POINT geometry of the ending vertex.

This inner query takes precedence over the next inner query, therefore other columns are ignored when startpoint and endpoint columns appears.

  • Ignored columns:
    • source
    • target

When identifiers of vertices are known

To use this inner query the columns geom, startpoint and endpoint should not be part of the set of columns.

Column Type Description
id BIGINT (Optional) 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.

Result Columns

Rreturns set of (id, in_edges, out_edges, x, y, geom)

Column Type Description
id BIGINT Identifier of the first end point vertex of the edge.
in_edges BIGINT[]
Array of identifiers of the edges that have the vertex id as first end point.
  • NULL When the id is not part of the inner query
out_edges BIGINT[]
Array of identifiers of the edges that have the vertex id as second end point.
  • NULL When the id is not part of the inner query
x FLOAT
X value of the POINT geometry
  • NULL When no geometry is provided
y FLOAT
Y value of the POINT geometry
  • NULL When no geometry is provided
geom POINT
Geometry of the POINT
  • NULL When no geometry is provided

Additional Examples

Example 1:Dryrun execution

To get the query generated used to get the vertex information, use dryrun := true.

The results can be used as base code to make a refinement based on the backend development needs.

SELECT  * FROM pgr_extractVertices(
    'SELECT id, the_geom AS geom FROM edge_table',
    dryrun := true);
NOTICE:
        WITH

        main_sql AS (
          SELECT id, the_geom AS geom FROM edge_table
        ),

        the_out AS (
          SELECT id::BIGINT AS out_edge, ST_StartPoint(geom) AS geom
          FROM main_sql
        ),

        agg_out AS (
          SELECT array_agg(out_edge ORDER BY out_edge) AS out_edges, ST_x(geom) AS x, ST_Y(geom) AS y, geom
          FROM the_out
          GROUP BY geom
        ),

        the_in AS (
          SELECT id::BIGINT AS in_edge, ST_EndPoint(geom) AS geom
          FROM main_sql
        ),

        agg_in AS (
          SELECT array_agg(in_edge ORDER BY in_edge) AS in_edges, ST_x(geom) AS x, ST_Y(geom) AS y, geom
          FROM the_in
          GROUP BY geom
        ),

        the_points AS (
          SELECT in_edges, out_edges, coalesce(agg_out.geom, agg_in.geom) AS geom
          FROM agg_out
          FULL OUTER JOIN agg_in USING (x, y)
        )

        SELECT row_number() over(ORDER BY ST_X(geom), ST_Y(geom)) AS id, in_edges, out_edges, ST_X(geom), ST_Y(geom), geom
        FROM the_points;
 id | in_edges | out_edges | x | y | geom
----+----------+-----------+---+---+------
(0 rows)

Example 2:Creating a routing topology
  1. Making sure the database does not have the vertices_table

    DROP TABLE IF EXISTS vertices_table;
    NOTICE:  table "vertices_table" does not exist, skipping
    DROP TABLE
    
  2. Cleaning up the columns of the rotuing topology to be created

    UPDATE edge_table
    SET source = NULL, target = NULL,
       x1 = NULL, y1 = NULL,
       x2 = NULL, y2 = NULL;
    UPDATE 18
    
  3. Creating the vertices table

    SELECT  * INTO vertices_table
    FROM pgr_extractVertices('SELECT id, the_geom AS geom FROM edge_table');
    SELECT 17
    
  4. Inspection of the vertices table

    SELECT *
    FROM vertices_table;
     id | in_edges | out_edges |       x        |  y  |                    geom
    ----+----------+-----------+----------------+-----+--------------------------------------------
      1 |          | {6}       |              0 |   2 | 010100000000000000000000000000000000000040
      2 |          | {17}      |            0.5 | 3.5 | 0101000000000000000000E03F0000000000000C40
      3 | {6}      | {7}       |              1 |   2 | 0101000000000000000000F03F0000000000000040
      4 | {17}     |           | 1.999999999999 | 3.5 | 010100000068EEFFFFFFFFFF3F0000000000000C40
      5 |          | {1}       |              2 |   0 | 010100000000000000000000400000000000000000
      6 | {1}      | {2,4}     |              2 |   1 | 01010000000000000000000040000000000000F03F
      7 | {4,7}    | {8,10}    |              2 |   2 | 010100000000000000000000400000000000000040
      8 | {10}     | {12,14}   |              2 |   3 | 010100000000000000000000400000000000000840
      9 | {14}     |           |              2 |   4 | 010100000000000000000000400000000000001040
     10 | {2}      | {3,5}     |              3 |   1 | 01010000000000000000000840000000000000F03F
     11 | {5,8}    | {9,11}    |              3 |   2 | 010100000000000000000008400000000000000040
     12 | {11,12}  | {13}      |              3 |   3 | 010100000000000000000008400000000000000840
     13 |          | {18}      |            3.5 | 2.3 | 01010000000000000000000C406666666666660240
     14 | {18}     |           |            3.5 |   4 | 01010000000000000000000C400000000000001040
     15 | {3}      | {16}      |              4 |   1 | 01010000000000000000001040000000000000F03F
     16 | {9,16}   | {15}      |              4 |   2 | 010100000000000000000010400000000000000040
     17 | {13,15}  |           |              4 |   3 | 010100000000000000000010400000000000000840
    (17 rows)
    
    
  5. Creating the routing topology on the edge table

    Updating the source information

    WITH
        out_going AS (
            SELECT id AS vid, unnest(out_edges) AS eid, x, y
            FROM vertices_table
        )
    UPDATE edge_table
    SET source = vid, x1 = x, y1 = y
    FROM out_going WHERE id = eid;
    UPDATE 18
    

    Updating the target information

    WITH
        in_coming AS (
            SELECT id AS vid, unnest(in_edges) AS eid, x, y
            FROM vertices_table
        )
    UPDATE edge_table
    SET target = vid, x2 = x, y2 = y
    FROM in_coming WHERE id = eid;
    UPDATE 18
    
  6. Inspection of the routing topology

    SELECT id, source, target, x1, y1, x2, y2
    FROM edge_table;
     id | source | target | x1  | y1  |       x2       | y2
    ----+--------+--------+-----+-----+----------------+-----
      6 |      1 |      3 |   0 |   2 |              1 |   2
     17 |      2 |      4 | 0.5 | 3.5 | 1.999999999999 | 3.5
      1 |      5 |      6 |   2 |   0 |              2 |   1
      4 |      6 |      7 |   2 |   1 |              2 |   2
      7 |      3 |      7 |   1 |   2 |              2 |   2
     10 |      7 |      8 |   2 |   2 |              2 |   3
     14 |      8 |      9 |   2 |   3 |              2 |   4
      2 |      6 |     10 |   2 |   1 |              3 |   1
      5 |     10 |     11 |   3 |   1 |              3 |   2
      8 |      7 |     11 |   2 |   2 |              3 |   2
     11 |     11 |     12 |   3 |   2 |              3 |   3
     12 |      8 |     12 |   2 |   3 |              3 |   3
     18 |     13 |     14 | 3.5 | 2.3 |            3.5 |   4
      3 |     10 |     15 |   3 |   1 |              4 |   1
      9 |     11 |     16 |   3 |   2 |              4 |   2
     16 |     15 |     16 |   4 |   1 |              4 |   2
     13 |     12 |     17 |   3 |   3 |              4 |   3
     15 |     16 |     17 |   4 |   2 |              4 |   3
    (18 rows)
    
    

See Also

Indices and tables