如何在函数pgr_dijkstra中使用循环

Question

I want to use a loop to calculate the distance traveled between two nodes 152 and 17720 (I use the function pgr_dijkstra) by deleting each time a cell. A cell contains several road links. the grid_edges_routard table contains the road links and the corresponding cell. Iwant to have for each blocked cell the distance traveled between the two nodes. I must use pgr_dijkstra to display in a second time the links traveled.

CREATE OR REPLACE FUNCTION get_dist_grid() 
 RETURNS TABLE (
 celref_blocked INT,
 dist INT
) AS $$
DECLARE 
    var_r record;
BEGIN
 FOR var_r IN(SELECT distinct(cellule)as cel from grid_edges_routard )  
 LOOP

 SELECT * FROM pgr_dijkstra('SELECT id, source, target,cost 
                    FROM road_routard.edges_vulnerabilite 
                    where id not in (select edge_id
                                                     from grid_edges_routard
                                                     where cellule=var_r)  ',152   ,17720, FALSE)
                 where edge=-1; 
     celref_blocked  := var_r.cel ;            

        RETURN NEXT;
 END LOOP;
END; $$ 
LANGUAGE 'plpgsql';

select get_dist_grid()

I have an error message: ERROR: column « var_r » does not exist. I use postgresql 9.5.

Answer 1

定义类型的记录的新变量（var_q），然后执行你的选择查询到你这样的定义的变量Execute 'SELECT * FROM pgr_dijkstra(''SELECT id, source, target,cost FROM road_routard.edges_vulnerabilite where id not in (select edge_id from grid_edges_routard where cellule='||var_r||') '',152 ,17720, FALSE) where edge=-1' into var_q这可能会产生一些错误，因为我们必须对内部查询使用引号，如果Execute 'SELECT * FROM pgr_dijkstra(''SELECT id, source, target,cost FROM road_routard.edges_vulnerabilite where id not in (select edge_id from grid_edges_routard where cellule='||var_r||') '',152 ,17720, FALSE) where edge=-1' into var_q引号，请尝试转义它不起作用，然后您可以像使用celref_blocked：= var_r.cel一样，使用out查询。