[postgis-users] PgRouting in PostGIS

[Nandorov]

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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