[pgrouting-users] assign_vertex_id usage in Workshop

[Daniel Kastl]

On Tue, Apr 9, 2013 at 7:28 PM, Luís de Sousa <luis.a.de.sousa at gmail.com>wrote:

> Hello again,
>
> In section 5 of the Workshop the assign_vertex_id function is used on a
> MULTILINESTRING column:
>
> http://workshop.pgrouting.org/chapters/topology.html#calculate-topology
>
> This function makes use of the st_startpoint function that can only take
> as input a LINESTRING. I worked around this by creating an extra column in
> the ways table, but I wonder what can be the usage may be of a network
> composed by MULTILINESTRING objects. Perhaps it would be better to simply
> change the data type used in this example.
>

Yes, this is another issue that comes with PostGIS 2.0.
You can change "multi" geometries into single geometry like this:

SELECT (ST_Dump(geom)).geom AS geom FROM <table>

or

ALTER TABLE <table> ALTER COLUMN geom
  SET DATA TYPE geometry(Linestring,4326) USING ST_GeometryN(geom, 1);

In general these are all LINESTRINGS, so it's no problem to convert.

With new release of pgRouting this will be fixed.

Daniel








-- 
Georepublic UG & Georepublic Japan
eMail: daniel.kastl at georepublic.de
Web: http://georepublic.de
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