在从本网站收到很多帮助后,我终于创建了一套完成我想要的工作的功能。谢谢你,但似乎有一个最后的问题,即高效的内存使用情况。这里是问题:
在postgreSQL 9.3中,使用postGIS 2.1和pgRouting 2.0,我创建了一个函数,它使用pgrouting函数pgr_trsp计算两点之间的路线并返回一个几何(Linestring)值。这里是代码:PostgreSQL的功能和内存问题
CREATE OR REPLACE FUNCTION fm_pgr2geom(edge1 integer, pos1 double precision, edge2 integer, pos2 double precision)
RETURNS geometry AS
$BODY$
--We have to do a routing query. And declare a cursor for it
DECLARE resc CURSOR FOR
SELECT * FROM pgr_trsp (
'SELECT * FROM th_2po_4pgr',
$1, $2, $3, $4, false, true);
doline geometry[];
temp_point geometry;
geom geometry;
temp_rec RECORD;
n integer;
BEGIN
--Append all the edges
FOR temp_rec IN SELECT * FROM pgr_trsp (
'SELECT * FROM th_2po_4pgr',
$1, $2, $3, $4, false, true) LOOP
doline := array_append(
doline, (SELECT map.geom_way FROM th_2po_4pgr map WHERE map.id = temp_rec.id2));
END LOOP;
--Remove 1st and last edge
n := array_length (doline, 1);
doline := doline [2:n-1];
--Find startpoint and append to doline
doline := array_prepend(
ST_LineInterpolatePoint((SELECT map.geom_way FROM th_2po_4pgr map WHERE map.id = $1),$2),doline);
--Append the endpoint
doline := array_append(
doline,ST_LineInterpolatePoint((SELECT map.geom_way FROM th_2po_4pgr map WHERE map.id = $3),$4));
geom := ST_MakeLine(doline);
RETURN geom;
EXCEPTION
WHEN SQLSTATE 'XX000' THEN RETURN NULL;
WHEN SQLSTATE '38001' THEN RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION fm_pgr2geom(integer, double precision, integer, double precision)
OWNER TO postgres;
该函数在另一个函数中用于批量更新具有几何结果的大型表(800k +)。这是供参考:
CREATE OR REPLACE FUNCTION fm_seqrouting()
RETURNS integer AS
$BODY$
--Declarations
DECLARE
r record;
i integer;
BEGIN
--CODE to calculate routes and update table
i := 0;
FOR r IN
SELECT veh_id
,dt
,map_edge_id AS map_id1
,map_edge_pos AS map_pos1
,lead(map_edge_id) OVER w AS map_id2
,lead(map_edge_pos) OVER w AS map_pos2
FROM taxilocs
WINDOW w AS (ORDER BY veh_id, dt)
LOOP
UPDATE taxilocs
SET geom_route = fm_pgr2geom (r.map_id1,r.map_pos1,r.map_id2,r.map_pos2)
WHERE r.veh_id = taxilocs.veh_id AND r.dt=taxilocs.dt;
i := i + 1;
END LOOP;
RETURN i;
END;
$BODY$
LANGUAGE plpgsql;
例外的情况是绝对必要的,因为他们处理某些情况下,一些数据从上述表丢失,或者路由路径无法找到。但是,它似乎导致了问题,即更新查询在几分钟后崩溃。我执行的一些分钟后收到的信息是:
ERROR: out of memory
SQL state: 53200
Detail: Failed on request of size 640000.
所以,问题是:如何有效地使用或重新编写此函数来更新我想要的表?有任何想法吗?
预先感谢您!
有什么当查询“崩溃”时收到的消息?你在什么版本的PostgreSQL?执行更新的函数在哪里崩溃? – Kuberchaun
@JustBob我用你提的信息更新了我的问题。也许你现在可以给我一些提示? –
你的桌子上有没有索引,你能提供DDL吗? PostgreSQL是为32位或64位编译的。我记得过去在32bit上有这样的问题的人,但在64bit上工作正常。 – Kuberchaun