基于pgrouting的最短路径规划

最近项目上有一个计算两点最短路径的需求，即就是类似于百度地图的路径规划问题，小编研究了一段时间，并参考了相关资料，基于postgresql+postgis+pgrouting实现了简单的路径规划，计算的结果是组成最短路径的所有线路的集合，话不多说，直接上主要的存储过程：

CREATE OR REPLACE FUNCTION public.pgr_shortest_road(
IN startx double precision,
IN starty double precision,
IN endx double precision,
IN endy double precision,
OUT road_name character varying,
OUT v_shpath character varying,
OUT cost double precision)
RETURNS SETOF record AS
$BODY$
declare
v_startLine geometry;--离起点最近的线
v_endLine geometry;--离终点最近的线
v_startTarget integer;--距离起点最近线的终点
v_endSource integer;--距离终点最近线的起点
v_statpoint geometry;--在v_startLine上距离起点最近的点
v_endpoint geometry;--在v_endLine上距离终点最近的点
v_res geometry;--最短路径分析结果
v_perStart float;--v_statpoint在v_res上的百分比
v_perEnd float;--v_endpoint在v_res上的百分比
v_rec record;
first_name varchar;
end_name varchar;
first_cost double precision;
end_cost double precision;
begin
--查询离起点最近的线
execute 'select geom,target,name from china_road where
ST_DWithin(geom,ST_Geometryfromtext(''point('|| startx ||' ' || starty||')''),0.01)
order by ST_Distance(geom,ST_GeometryFromText(''point('|| startx ||' '|| starty ||')'')) limit 1'
into v_startLine ,v_startTarget,first_name;
--查询离终点最近的线
execute 'select geom,source,name from china_road
where ST_DWithin(geom,ST_Geometryfromtext(''point('|| endx || ' ' || endy ||')''),0.01)
order by ST_Distance(geom,ST_GeometryFromText(''point('|| endx ||' ' || endy ||')'')) limit 1'
into v_endLine,v_endSource,end_name;
--如果没找到最近的线，就返回null
if (v_startLine is null) or (v_endLine is null) then
return;
end if ;
select ST_ClosestPoint(v_startLine, ST_Geometryfromtext('point('|| startx ||' ' || starty ||')')) into v_statpoint;
select ST_ClosestPoint(v_endLine, ST_GeometryFromText('point('|| endx ||' ' || endy ||')')) into v_endpoint; 

--计算距离起点最近线上的点在该线中的位置
select ST_Line_Locate_Point(st_linemerge(v_startLine), v_statpoint) into v_perStart;

select ST_Line_Locate_Point(st_linemerge(v_endLine), v_endpoint) into v_perEnd;

select ST_Distance_Sphere(v_statpoint,ST_PointN(ST_GeometryN(v_startLine,1), ST_NumPoints(ST_GeometryN(v_startLine,1)))) into first_cost;

select ST_Distance_Sphere(ST_PointN(ST_GeometryN(v_endLine,1),1),v_endpoint) into end_cost; 

if (ST_Intersects(st_geomfromtext('point('|| startx ||' '|| starty ||') '), v_startLine) and ST_Intersects(st_geomfromtext('point('|| endx ||' '|| endy ||') '), v_startLine)) then
select ST_Distance_Sphere(v_statpoint, v_endpoint) into first_cost;

select ST_Line_Locate_Point(st_linemerge(v_startLine), v_endpoint) into v_perEnd;
for v_rec in
select ST_Line_SubString(st_linemerge(v_startLine), v_perStart,v_perEnd) as point,COALESCE(end_name,'无名路') as name,end_cost as cost loop
v_shPath:= ST_AsGeoJSON(v_rec.point);
cost:= v_rec.cost;
road_name:= v_rec.name;
return next;
end loop;
return;
end if;
--最短路径
for v_rec in
(select ST_Line_SubString(st_linemerge(v_startLine),v_perStart,1) as point,COALESCE(first_name,'无名路') as name,first_cost as cost
union all
SELECT st_linemerge(b.geom) as point,COALESCE(b.name,'无名路') as name,b.length as cost
FROM pgr_dijkstra(
'SELECT gid as id, source, target, length as cost FROM china_road
where st_intersects(geom,st_buffer(st_linefromtext(''linestring('||startx||' ' || starty ||','|| endx ||' ' || endy ||')''),0.05))',
v_startTarget, v_endSource , false
) a, china_road b
WHERE a.edge = b.gid
union all
select ST_Line_SubString(st_linemerge(v_endLine),0,v_perEnd) as point,COALESCE(end_name,'无名路') as name,end_cost as cost)
loop
v_shPath:= ST_AsGeoJSON(v_rec.point);
cost:= v_rec.cost;
road_name:= v_rec.name;
return next;
end loop;
end;
$BODY$
LANGUAGE plpgsql VOLATILE STRICT;

如有问题，欢迎留言交流！