什麼是路徑模型,如何使用路徑模型 - ApsaraDB RDS

路徑資料是由Edge和Node構成的幾何網狀圖，主要用於構建道路和交通網路。

概述

Ganos Networking是對象關係型資料庫PostgreSQL的一個擴充，提供了一系列的函數和預存程序，用於根據代價模型尋找最快、最短甚至是最優的路徑。如果代價是時間，則最佳路線為最快路線。如果代價是距離，則最佳路徑為最短路徑。路徑模型用於解決基於道路網的路徑規劃問題、電子地圖GPS導航路徑搜尋規劃問題、路由問題等。路徑模型完全相容PGRouting介面，支援已有應用的平滑遷移。

快速入門

建立擴充
Create Extension Ganos_Networking with schema public cascade;

建立表

CREATE TABLE edge_table (
    id BIGSERIAL,
    dir character varying,
    source BIGINT,
    target BIGINT,
    cost FLOAT,
    reverse_cost FLOAT,
    capacity BIGINT,
    reverse_capacity BIGINT,
    category_id INTEGER,
    reverse_category_id INTEGER,
    x1 FLOAT,
    y1 FLOAT,
    x2 FLOAT,
    y2 FLOAT,
    the_geom geometry
);

插入記錄

INSERT INTO edge_table (
    category_id, reverse_category_id,
    cost, reverse_cost,
    capacity, reverse_capacity,
    x1, y1,
    x2, y2) VALUES
(3, 1,    1,  1,  80, 130,   2,   0,    2, 1),
(3, 2,   -1,  1,  -1, 100,   2,   1,    3, 1),
(2, 1,   -1,  1,  -1, 130,   3,   1,    4, 1),
(2, 4,    1,  1, 100,  50,   2,   1,    2, 2),
(1, 4,    1, -1, 130,  -1,   3,   1,    3, 2),
(4, 2,    1,  1,  50, 100,   0,   2,    1, 2),
(4, 1,    1,  1,  50, 130,   1,   2,    2, 2),
(2, 1,    1,  1, 100, 130,   2,   2,    3, 2),
(1, 3,    1,  1, 130,  80,   3,   2,    4, 2),
(1, 4,    1,  1, 130,  50,   2,   2,    2, 3),
(1, 2,    1, -1, 130,  -1,   3,   2,    3, 3),
(2, 3,    1, -1, 100,  -1,   2,   3,    3, 3),
(2, 4,    1, -1, 100,  -1,   3,   3,    4, 3),
(3, 1,    1,  1,  80, 130,   2,   3,    2, 4),
(3, 4,    1,  1,  80,  50,   4,   2,    4, 3),
(3, 3,    1,  1,  80,  80,   4,   1,    4, 2),
(1, 2,    1,  1, 130, 100,   0.5, 3.5,  1.999999999999,3.5),
(4, 1,    1,  1,  50, 130,   3.5, 2.3,  3.5,4);

更新表屬性

UPDATE edge_table SET the_geom = st_makeline(st_point(x1,y1),st_point(x2,y2)),
dir = CASE WHEN (cost>0 AND reverse_cost>0) THEN 'B'  
           WHEN (cost>0 AND reverse_cost<0) THEN 'FT'  
           WHEN (cost<0 AND reverse_cost>0) THEN 'TF'  
           ELSE '' END;

建立拓撲

SELECT pgr_createTopology('edge_table',0.001);

查詢最短路徑

-- 使用dijkstra演算法查詢最短路徑
SELECT * FROM pgr_dijkstra(
    'SELECT id, source, target, cost, reverse_cost FROM edge_table',
    2, 3
);

 seq | path_seq | node | edge | cost | agg_cost
-----+----------+------+------+------+----------
   1 |        1 |    2 |    4 |    1 |        0
   2 |        2 |    5 |    8 |    1 |        1
   3 |        3 |    6 |    9 |    1 |        2
   4 |        4 |    9 |   16 |    1 |        3
   5 |        5 |    4 |    3 |    1 |        4
   6 |        6 |    3 |   -1 |    0 |        5
(6 rows)

-- 使用astar演算法查詢最短路徑
SELECT * FROM pgr_astar(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    2, 12,
    directed := false, heuristic := 2);

 seq | path_seq | node | edge | cost | agg_cost
-----+----------+------+------+------+----------
   1 |        1 |    2 |    2 |    1 |        0
   2 |        2 |    3 |    3 |    1 |        1
   3 |        3 |    4 |   16 |    1 |        2
   4 |        4 |    9 |   15 |    1 |        3
   5 |        5 |   12 |   -1 |    0 |        4
(5 rows)

-- 使用trsp 路徑演算法
SELECT * FROM pgr_trsp(
        'SELECT id::INTEGER, source::INTEGER, target::INTEGER, cost FROM edge_table',
        2, 7, false, false,
        'SELECT to_cost, target_id::int4,
        from_edge || coalesce('','' || via_path, '''') AS via_path
        FROM restrictions'
    );

 seq | id1 | id2 | cost
-----+-----+-----+------
   0 |   2 |   4 |    1
   1 |   5 |  10 |    1
   2 |  10 |  12 |    1
   3 |  11 |  11 |    1
   4 |   6 |   8 |    1
   5 |   5 |   7 |    1
   6 |   8 |   6 |    1
   7 |   7 |  -1 |    0
(8 rows)

刪除擴充

Drop Extension Ganos_Networking cascade;

SQL參考

詳細SQL手冊請參見pgrouting 官方文檔。