pgr_extractVertices – Propuesto¶
pgr_extractVertices — Extrae la información de los vértices
Advertencia
Funciones propuestas para la próxima versión mayor.
No están oficialmente en la versión actual.
Es probable que oficialmente formen parte del próximo lanzamiento:
Las funciones hacen uso de ENTEROS y FLOTANTES
Probablemente el nombre no cambie. (Pero todavía puede)
Es posible que la firma no cambie. (Pero todavía puede)
Probablemente la funcionalidad no cambie. (Pero todavía puede)
Se han hecho pruebas con pgTap. Pero tal vez se necesiten más.
Es posible que la documentación necesite un refinamiento.
Disponibilidad
Versión 3.3.0
Clasicado como función propuesta
Versión 3.0.0
Nueva función experimental
Descripción¶
Esta es una función auxiliar para extraer la información de vértices del conjunto de aristas de un grafo.
Cuando se proporciona el identificador de arista, también se calcularán las aristas de entrada y salida
Firmas¶
dryrun])(id, in_edges, out_edges, x, y, geom)- Ejemplo:
Extraer la información del vértice
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)
Parámetros¶
Parámetro |
Tipo |
Descripción |
|---|---|---|
|
SQL de aristas como se describe a continuación |
Parámetros opcionales¶
Parámetro |
Tipo |
x Defecto |
Descripción |
|---|---|---|---|
|
|
|
|
Consultas Internas¶
SQL aristas¶
Cuando se conoce la geometría de línea¶
Columna |
Tipo |
Descripción |
|---|---|---|
|
|
(Opcional) identificador de la arista. |
|
|
Geometría de la arista. |
Esta consulta interna tiene prioridad sobre las dos consultas internas siguientes, por lo que se omiten otras columnas cuando aparece la columna “”geom””.
Columnas ignoradas:
startpointendpointsourcetarget
Cuando se conoce la geometría de vértices¶
Para utilizar esta consulta interna, la columna geom no debe formar parte del conjunto de columnas.
Columna |
Tipo |
Descripción |
|---|---|---|
|
|
(Opcional) identificador de la arista. |
|
|
Geometría POINT del vértice inicial. |
|
|
Geometría POINT del vértice final. |
Esta consulta interna tiene prioridad sobre la siguiente consulta interna, por lo que otras columnas son ignoradas cuando aparecen las columnas startpoint y endpoint.
Columnas ignoradas:
sourcetarget
Cuando se conocen identificadores de vértices¶
Para utilizar esta consulta interna, las columnas geom, startpoint y endpoint no deben formar parte del conjunto de columnas.
Columna |
Tipo |
Descripción |
|---|---|---|
|
|
(Opcional) identificador de la arista. |
|
|
Identificador del primer vértice de la arista. |
|
|
Identificador del segundo vértice de la arista. |
Columnas de Resultados¶
Columna |
Tipo |
Descripción |
|---|---|---|
|
|
Identificador de vértice |
|
|
Arreglo de identificadores de las aristas que tienen el vértice
|
|
|
Arreglo de identificadores de las aristas que tienen el vértice
|
|
|
Valor X de la geometría del punto
|
|
|
Valor X de la geometría del punto
|
|
|
Geometría del punto
|
Ejemplos Adicionales¶
Ejecución de Dryrun¶
Para obtener la consulta generada que se usa para obtener la información de vértices, utilice dryrun := true.
Los resultados se pueden usar como código base para realizar un refinamiento basado en las necesidades de desarrollo de back-end.
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)
Creación de una topología de ruteo¶
Asegurarse de que la base de datos no tiene vertices_table¶
DROP TABLE IF EXISTS vertices_table;
NOTICE: table "vertices_table" does not exist, skipping
DROP TABLE
Limpieza de las columnas de la topología de ruteo que se creará¶
UPDATE edges
SET source = NULL, target = NULL,
x1 = NULL, y1 = NULL,
x2 = NULL, y2 = NULL;
UPDATE 18
Crear la tabla de vértices¶
When the
LINESTRINGhas a SRID then usegeom::geometry(POINT, <SRID>)For big edge tables that are been prepared,
Create it as
UNLOGGEDandAfter 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
Inspeccionar la tabla de vértices¶
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)
Creación de la topología de ruteo en la tabla de aristas¶
Actualizar de la información de source
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
Actualización de la información de target
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
Inspección de la topología de ruteo¶
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)
Topología generada¶
Crossing edges¶
To get the crossing edges:
SELECT a.id, b.id
FROM edges AS a, edges AS b
WHERE a.id < b.id AND st_crosses(a.geom, b.geom);
id | id
----+----
13 | 18
(1 row)
That information is correct, for example, when in terms of vehicles, is it a tunnel or bride crossing over another road.
It might be incorrect, for example:
When it is actually an intersection of roads, where vehicles can make turns.
When in terms of electrical lines, the electrical line is able to switch roads even on a tunnel or bridge.
When it is incorrect, it needs fixing:
For vehicles and pedestrians
If the data comes from OSM and was imported to the database using
osm2pgrouting, the fix needs to be done in the OSM portal and the data imported again.In general when the data comes from a supplier that has the data prepared for routing vehicles, and there is a problem, the data is to be fixed from the supplier
For very specific applications
The data is correct when from the point of view of routing vehicles or pedestrians.
The data needs a local fix for the specific application.
Once analyzed one by one the crossings, for the ones that need a local fix, the edges need to be split.
SELECT ST_AsText((ST_Dump(ST_Split(a.geom, b.geom))).geom)
FROM edges AS a, edges AS b
WHERE a.id = 13 AND b.id = 18
UNION
SELECT ST_AsText((ST_Dump(ST_Split(b.geom, a.geom))).geom)
FROM edges AS a, edges AS b
WHERE a.id = 13 AND b.id = 18;
st_astext
---------------------------
LINESTRING(3.5 2.3,3.5 3)
LINESTRING(3 3,3.5 3)
LINESTRING(3.5 3,4 3)
LINESTRING(3.5 3,3.5 4)
(4 rows)
The new edges need to be added to the edges table, the rest of the attributes need to be updated in the new edges, the old edges need to be removed and the routing topology needs to be updated.
Adding split edges¶
For each pair of crossing edges a process similar to this one must be performed.
The columns inserted and the way are calculated are based on the application. For example, if the edges have a trait name, then that column is to be copied.
Para llos cálculos de pgRouting
factor based on the position of the intersection of the edges can be used to adjust the
costandreverse_costcolumns.Capacity information, used on the Flow - Familia de funciones functions does not need to change when splitting edges.
WITH
first_edge AS (
SELECT (ST_Dump(ST_Split(a.geom, b.geom))).path[1],
(ST_Dump(ST_Split(a.geom, b.geom))).geom,
ST_LineLocatePoint(a.geom,ST_Intersection(a.geom,b.geom)) AS factor
FROM edges AS a, edges AS b
WHERE a.id = 13 AND b.id = 18),
first_segments AS (
SELECT path, first_edge.geom,
capacity, reverse_capacity,
CASE WHEN path=1 THEN factor * cost
ELSE (1 - factor) * cost END AS cost,
CASE WHEN path=1 THEN factor * reverse_cost
ELSE (1 - factor) * reverse_cost END AS reverse_cost
FROM first_edge , edges WHERE id = 13),
second_edge AS (
SELECT (ST_Dump(ST_Split(b.geom, a.geom))).path[1],
(ST_Dump(ST_Split(b.geom, a.geom))).geom,
ST_LineLocatePoint(b.geom,ST_Intersection(a.geom,b.geom)) AS factor
FROM edges AS a, edges AS b
WHERE a.id = 13 AND b.id = 18),
second_segments AS (
SELECT path, second_edge.geom,
capacity, reverse_capacity,
CASE WHEN path=1 THEN factor * cost
ELSE (1 - factor) * cost END AS cost,
CASE WHEN path=1 THEN factor * reverse_cost
ELSE (1 - factor) * reverse_cost END AS reverse_cost
FROM second_edge , edges WHERE id = 18),
all_segments AS (
SELECT * FROM first_segments
UNION
SELECT * FROM second_segments)
INSERT INTO edges
(capacity, reverse_capacity,
cost, reverse_cost,
x1, y1, x2, y2,
geom)
(SELECT capacity, reverse_capacity, cost, reverse_cost,
ST_X(ST_StartPoint(geom)), ST_Y(ST_StartPoint(geom)),
ST_X(ST_EndPoint(geom)), ST_Y(ST_EndPoint(geom)),
geom
FROM all_segments);
INSERT 0 4
Añadiendo nuevos vértices¶
After adding all the split edges required by the application, the newly created vertices need to be added to the vertices table.
INSERT INTO vertices (in_edges, out_edges, x, y, geom)
(SELECT nv.in_edges, nv.out_edges, nv.x, nv.y, nv.geom
FROM pgr_extractVertices('SELECT id, geom FROM edges') AS nv
LEFT JOIN vertices AS v USING(geom) WHERE v.geom IS NULL);
INSERT 0 1
Actualizar la topología de aristas¶
/* -- set the source information */
UPDATE edges AS e
SET source = v.id
FROM vertices AS v
WHERE source IS NULL AND ST_StartPoint(e.geom) = v.geom;
UPDATE 4
/* -- set the target information */
UPDATE edges AS e
SET target = v.id
FROM vertices AS v
WHERE target IS NULL AND ST_EndPoint(e.geom) = v.geom;
UPDATE 4
Removing the surplus edges¶
Once all significant information needed by the application has been transported to the new edges, then the crossing edges can be deleted.
DELETE FROM edges WHERE id IN (13, 18);
DELETE 2
There are other options to do this task, like creating a view, or a materialized view.
Actializar la topología de vértices¶
To keep the graph consistent, the vertices topology needs to be updated
UPDATE vertices AS v SET
in_edges = nv.in_edges, out_edges = nv.out_edges
FROM (SELECT * FROM pgr_extractVertices('SELECT id, geom FROM edges')) AS nv
WHERE v.geom = nv.geom;
UPDATE 18
Checking for crossing edges¶
There are no crossing edges on the graph.
SELECT a.id, b.id
FROM edges AS a, edges AS b
WHERE a.id < b.id AND st_crosses(a.geom, b.geom);
id | id
----+----
(0 rows)
Grafos sin geometrías¶
Usando este diseño de tabla para este ejemplo:
CREATE TABLE wiki (
id SERIAL,
source INTEGER,
target INTEGER,
cost INTEGER);
CREATE TABLE
Introduzca los datos¶
INSERT INTO wiki (source, target, cost) VALUES
(1, 2, 7), (1, 3, 9), (1, 6, 14),
(2, 3, 10), (2, 4, 15),
(3, 6, 2), (3, 4, 11),
(4, 5, 6),
(5, 6, 9);
INSERT 0 9
En cuentre el camino más corto¶
Para resolver el ejemplo se usa pgr_dijkstra:
SELECT * FROM pgr_dijkstra(
'SELECT id, source, target, cost FROM wiki',
1, 5, false);
seq | path_seq | start_vid | end_vid | node | edge | cost | agg_cost
-----+----------+-----------+---------+------+------+------+----------
1 | 1 | 1 | 5 | 1 | 2 | 9 | 0
2 | 2 | 1 | 5 | 3 | 6 | 2 | 9
3 | 3 | 1 | 5 | 6 | 9 | 9 | 11
4 | 4 | 1 | 5 | 5 | -1 | 0 | 20
(4 rows)
Para ir de \(1\) a \(5\) el camino que atraviesa los siguientes vértices: \(1 \rightarrow 3 \rightarrow 6 \rightarrow 5\)
![graph G {
rankdir="LR";
1 [color="red"];
5 [color="green"];
1 -- 2 [label=" (7)"];
5 -- 6 [label=" (9)", color="blue"];
1 -- 3 [label=" (9)", color="blue"];
1 -- 6 [label=" (14)"];
2 -- 3 [label=" (10)"];
2 -- 4 [label=" (13)"];
3 -- 4 [label=" (11)"];
3 -- 6 [label=" (2)", color="blue"];
4 -- 5 [label=" (6)"];
}](_images/graphviz-7095ca58fc489e099e284f23a9e49787441fc104.png)
Información de vertices¶
Para obtener la información de los vértices, use pgr_extractVertices – Propuesto
SELECT id, in_edges, out_edges
FROM pgr_extractVertices('SELECT id, source, target FROM wiki');
id | in_edges | out_edges
----+----------+-----------
3 | {2,4} | {6,7}
5 | {8} | {9}
4 | {5,7} | {8}
2 | {1} | {4,5}
1 | | {1,2,3}
6 | {3,6,9} |
(6 rows)
Ver también¶
Índices y tablas