[postgis-users] PgRouting in PostGIS

[Nandorov]

i could resolved it doing

BEGIN TRANSACTION;
DROP TABLE IF EXISTS shortest_path_table_2;
CREATE TABLE shortest_path_table_2(gid int4) with oids;
SELECT AddGeometryColumn('','shortest_path_table_2', 'the_geom', -1,
'MULTILINESTRING', 2 );
INSERT INTO shortest_path_table_2(the_geom) 
select the_geom from tb_mygeom
where start_node in (
select vertex_id from shortest_path('SELECT
the_geom,id,source,target,x1,y1,x2,y2,cost,reverse_cost from mygeom where
is_blocked != ''Y'' '
,3989 ,145,true,true) )
and end_node in (
select vertex_id from shortest_path('SELECT
the_geom,id,source,target,x1,y1,x2,y2,cost,reverse_cost from mygeom where
is_blocked != ''Y'' '
,3989 ,145,true,true)
);
COMMIT

i the coordinates, but i dont know if that might affect the performance.



Nandorov wrote:
> 
> Hi Anton,
> i have a problem when applying where clause in the sql parameter for
> shortest_path function. Function seems to work well but how do i recover
> the coordinates?
> 
> i used to do this way, for example
> select * from shortest_path('SELECT
> id,source,target,x1,y1,x2,y2,cost,reverse_cost from tb_mygeom',3989
> ,145,true,true); to verify and then applied:
> insert into my_temptable(geom)
> select the_geom from dijkstra_sp_directed('tb_mygeom',3989,145,true,true);
> to recover the coordinates.
> 
> Now i applied 
> select * from shortest_path('SELECT
> id,source,target,x1,y1,x2,y2,cost,reverse_cost from tb_mygeom where
> isBlocked != ''Y'' ',3989 ,145,true,true);
> the functions seems to work, but i dont know how to get the coordinates,
> because if i apply dijkstra_sp_directed i can't filter there. I tried 
> 
> INSERT INTO shortest_path_table_2(the_geom) 
> select the_geom from tb_mygeom
> where gid in (
> select vertex_id from shortest_path('SELECT
> the_geom,id,source,target,x1,y1,x2,y2,cost,reverse_cost from
> full_calleslima where is_blocked != ''Y'' '
> ,3989 ,145,true,true) );
> 
> but it returns a messy format, no linked vertix
> 
> thanks a lot
> 
> 
> 
> 
> Anton A. Patrushev wrote:
>> 
>> Hi Fernando,
>> 
>> Of course you can use any SQL query with any filters you wish.
>> That's actually what pgRouting was made for!
>> 
>> Please read this:
>> http://pgrouting.postlbs.org/wiki/Dijkstra
>> http://pgrouting.postlbs.org/wiki/AStar
>> http://pgrouting.postlbs.org/wiki/ShootingStar
>> 
>> Anton.
>> 
>> On 9/24/08, Nandorov <nandorov at gmail.com> wrote:
>>>
>>>  hi,
>>>  thanks Anton for your answer at pgrouting forum. i'm goingo to reply
>>> here i
>>>  hope it's ok.
>>>
>>>  Hi Fernando,
>>>
>>>  I think I answered you already in the PostGIS mailing list.
>>>  Anyway, it is worth to repeat. You can block edges by assigning high
>>> value
>>>  to cost field. Or, if you wish, you can add one more field, let's say,
>>> of
>>>  boolean type and name it is_blocked, and then use core routing function
>>> (not
>>>  wrapper), where you can limit your search area with non-blocked edges
>>> only -
>>>  "SELECT ... WHERE NOT is_blocked".
>>>
>>>  So i the input sql statement at shortest path function can include
>>> where
>>>  filters? sounds nice. i'm going to try it later (00:16 here lol)
>>>
>>>  thanks a lot
>>>
>>>
>>>
>>>  Anton A. Patrushev wrote:
>>>  >
>>>  > Hi,
>>>  >
>>>  > Of course you can. You can put any float value as a cost. And if a
>>>  > cost of an edge is high enough comparing to other costs, algorithm
>>>  > will prefer not to pass through that edge.
>>>  >
>>>  > Anton.
>>>  >
>>>  > On 9/24/08, Nandorov <nandorov at gmail.com> wrote:
>>>  >>
>>>  >>  can i block some segments? for example cad gives the posibility to
>>> put a
>>>  >> max
>>>  >>  resistance value, let's say it's 100. So if the resistance of your
>>>  >> segment
>>>  >>  is 100 that segment is blocked and you cannot go thorught this way.
>>> if
>>>  >> this
>>>  >>  possible with pgrouting?
>>>  >>
>>>  >>  thanks!
>>>  >>
>>>  >>
>>>  >>
>>>  >>  Stephen Woodbridge wrote:
>>>  >>  >
>>>  >>  > Nandorov wrote:
>>>  >>  >> hi,
>>>  >>  >> i've tried pgrouting algorithms and works pretty well. However,
>>> i
>>>  >> dont
>>>  >>  >> know
>>>  >>  >> exactly the way they applied "the resistance" of a way
>>> (represented
>>>  >> by a
>>>  >>  >> multilinestring). has someone worked  with pgrouting before? and
>>> know
>>>  >> if
>>>  >>  >> i
>>>  >>  >> can modify their algorithms to adapt them to my requirements?
>>>  >>  >>
>>>  >>  >> thanks
>>>  >>  >
>>>  >>  > "the resistance" is applied as a "cost" to traverse the segment.
>>> All
>>>  >>  > cost must be positive. You can use length of the segment as cost
>>> for
>>>  >>  > shortest distance. or you can compute and assign a cost value
>>> based on
>>>  >>  > other attributes.
>>>  >>  >
>>>  >>  > -Steve
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>>>  >>
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