postgresql+postgis+pgrouting实现最短路径查询(1)---线数据的处理和建立拓扑

2018/04/28 16:00
阅读数 735

1、ALTER TABLE beijing_line ADD COLUMN source integer;  

ALTER TABLE beijing_line ADD COLUMN target integer;  

ALTER TABLE beijing_line ADD COLUMN length double precision;  

UPDATE beijing_line SET length = ST_Length(the_geom);

 

ps:执行createTopology这个函数之前一定得对数据库执行以下三句sql查询:

CREATE EXTENSION postgis;

CREATE EXTENSION postgis_topology;

CREATE EXTENSION fuzzystrmatch;

2、select pgr_createTopology('beijing_line',0.001,source:='source',id:='gid',target:='target',the_geom:='the_geom');

select pgr_createTopology('beijing_line',0.1,source:='source',id:='gid',target:='target',the_geom:='the_geom’);

把容差值设置的大一点,可能结果会好点

3、   SELECT * FROM pgr_dijkstra('  

                    SELECT gid as id,  

                             source::integer,  

                             target::integer,  

                             length::double precision as cost  

                             FROM beijing_line',  

                    30, 60, false, false); 

无查询结果就执行下面这几个试一试,也可能是两点之间就没有路径

select source from beijing_line;

select target from beijing_line;

select length from beijing_line;

 

4、查询所经过的所有点:

SELECT st_astext(the_geom) FROM pgr_dijkstra('

 

SELECT gid AS id,                   

 

source::integer,                       

 

target::integer,                      

 

length::double precision AS cost

 

FROM beijing_line',

 

30, 60, false, false) as di

 

join beijing_line pt

 

on di.id2 = pt.gid;

5、将路径写入一个几何文件内:

SELECT seq, id1 AS node, id2 AS edge, cost,the_geom into dijkstra_res FROM pgr_dijkstra('

 

SELECT gid AS id,                    

 

source::integer,                       

 

target::integer,                      

 

length::double precision AS cost

 

FROM beij hbs90.cn ing_line',

 

30, 60, false, false) as di

 

join beijing_line pt

 

on di.id2 = pt. senta77.com gid;

经历过以上的步骤,如果一切顺利,应该能看到结果,这里不再截图。这时初步的准备工作已经完成。

参考博文如下():

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