pgr_extractVertices

pgr_extractVertices - Extracts the vertices information

Availability

Version 3.8.0

  • Error messages adjustment.

  • Function promoted to official.

Version 3.3.0

  • Function promoted to proposed.

Version 3.0.0

  • New experimental function.

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

Boost Graph inside Boost Graph Inside

Signatures

pgr_extractVertices( Edges SQL , [ dryrun ])
RETURNS SETOF (id, in_edges, out_edges, x, y, geom)
OR EMPTY SET
Example :

Extracting the vertex information 

SELECT  * FROM pgr_extractVertices(
  'SELECT id, geom FROM edges');
 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

Edges SQL as described below

Optional parameters

Parameter

Type

Default

Description

dryrun

BOOLEAN

false

  • When true do not process and get in a NOTICE the resulting query.

Inner Queries

Edges SQL

When line geometry is known

Column

Type

Description

id

BIGINT

(Optional) identifier of the edge.

geom

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

Column

Type

Description

id

BIGINT

Vertex identifier

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

X 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

Dry run 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, geom FROM edges',
  dryrun => true);
NOTICE:
        WITH

        main_sql AS (
          SELECT id, geom FROM edges
        ),

        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)

Create a routing topology

Make 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
Clean up the columns of the routing topology to be created 
UPDATE edges
SET source = NULL, target = NULL,
x1 = NULL, y1 = NULL,
x2 = NULL, y2 = NULL;
UPDATE 18
Create the vertices table

  • When the LINESTRING has a SRID then use geom::geometry(POINT, )

  • For big edge tables that are been prepared,

    • Create it as UNLOGGED and

    • After the table is created ALTER TABLE .. SET LOGGED 

SELECT  * INTO vertices_table
FROM pgr_extractVertices('SELECT id, geom FROM edges ORDER BY id');
SELECT 17
Inspect 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)
Create 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 edges
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 edges
SET target = vid, x2 = x, y2 = y
FROM in_coming WHERE id = eid;
UPDATE 18
Inspect the routing topology 
SELECT id, source, target, x1, y1, x2, y2
FROM edges ORDER BY id;
 id  source  target  x1   y1         x2        y2
----+--------+--------+-----+-----+----------------+-----
  1       5       6    2    0               2    1
  2       6      10    2    1               3    1
  3      10      15    3    1               4    1
  4       6       7    2    1               2    2
  5      10      11    3    1               3    2
  6       1       3    0    2               1    2
  7       3       7    1    2               2    2
  8       7      11    2    2               3    2
  9      11      16    3    2               4    2
 10       7       8    2    2               2    3
 11      11      12    3    2               3    3
 12       8      12    2    3               3    3
 13      12      17    3    3               4    3
 14       8       9    2    3               2    4
 15      16      17    4    2               4    3
 16      15      16    4    1               4    2
 17       2       4  0.5  3.5  1.999999999999  3.5
 18      13      14  3.5  2.3             3.5    4
(18 rows)
images/Fig1-originalData.png

Generated topology

See Also

Indices and tables