Using pgrouting and algorithms in PostgreSQL?

I am trying my first pgrouting in a roads shape file i load it in postgresql first, the table has osm_id gid name ref type oneway maxspeed

after i add columns source and target in table

ALTER TABLE roads ADD COLUMN "source" integer;
ALTER TABLE roads ADD COLUMN "target" integer;

After i make the topology with function

SELECT pgr_createTopology('roads', 0.0001, 'geom', 'gid');

make indexis

CREATE INDEX roads_source_idx ON roads("source");
CREATE INDEX roads_target_idx ON roads("target");

Add cost column and count the cost with geom colum use ST_LENGTH method

ALTER TABLE roads ADD COLUMN length double precision;
UPDATE roads SET length = ST_LENGTH(geom);

Add reverse cost colume and count it

ALTER TABLE roads ADD COLUMN reverse_cost double precision;
UPDATE roads SET reverse_cost = length;

last i run the distrack query is running in postgres if i try to run this query in QGIS is not runnig this is the first problem.

SELECT seq, id1 AS node, id2 AS edge, cost FROM pgr_dijkstra('
                SELECT gid AS id,
                         source::integer,
                         target::integer,
                         shape_leng::double precision AS cost
                        FROM roads',
                30, 300, false, false);

after i try to use A* i count the x1 y1 x2 y2 but the colums is empty and i dont know why insert the colums with this queries ALTER TABLE roads ADD COLUMN x1 double precision; ALTER TABLE roads ADD COLUMN y1 double precision; ALTER TABLE roads ADD COLUMN x2 double precision; ALTER TABLE roads ADD COLUMN y2 double precision; after i use this queries to field them but the columns stiil empty after execute

UPDATE roads SET x1 = ST_x(ST_startpoint(geom));
UPDATE roads SET y1 = ST_y(ST_startpoint(geom));
UPDATE roads SET x2 = ST_x(ST_endpoint(geom));
UPDATE roads SET y2 = ST_y(ST_endpoint(geom));

I read in net same versions have problem with startpoint and endpoint and i use the PointN but i still take empty columns

UPDATE roads SET x1 = ST_x(ST_PointN(geom, 1));
UPDATE roads SET y1 = ST_y(ST_PointN(geom, 1));
UPDATE roads SET x2 = ST_x(ST_PointN(geom, ST_NumPoints(geom)));
UPDATE roads SET y2 = ST_y(ST_PointN(geom, ST_NumPoints(geom)));

and the query for A*

SELECT seq, id1 AS node, id2 AS edge, cost FROM pgr_astar('
                SELECT gid AS id,
                         source::integer,
                         target::integer,
                         shape_leng::double precision AS cost,
                         x1, y1, x2, y2
                        FROM roads',
                30, 60, false, false);

how i show the routing in QGIS from postgresql i did it, but i still have problem with A* x1,y1 & x2,y2 after the update is still empty the columns x1 y1 x2 y2?

i try to use this queries but the x2y2 is not filling

UPDATE roads SET x1 = ST_X(ST_StartPoint(ST_geometryN(geom,1)));
UPDATE roads SET y1 = ST_Y(ST_StartPoint(ST_geometryN(geom,1)));
UPDATE roads SET x2 = ST_X(ST_EndPoint(ST_geometryN(geom,ST_NumPoints(geom))));
UPDATE roads SET y2 = ST_Y(ST_EndPoint(ST_geometryN(geom,ST_NumPoints(geom))));

Please if anyone can help me