[postgis-users] St_boundary and illegal argument exception

[Kevin Neufeld]

I'm not sure exactly what you are trying to do, but yes, ST_Boundary 
does extract linework (aka. the boundary) from a polygon.

SELECT ST_AsText(ST_Boundary('POLYGON((0 0, 1 1, 1 0, 0 0))'::geometry));
          st_astext         
-----------------------------
 LINESTRING(0 0,1 1,1 0,0 0)
(1 row)

Can you isolate the geometry that is causing you grief?
-- Kevin


George Silva wrote:
> Hello everyone.
>
> I'm trying to build a function that will transforma one polygon into 
> many lines. I have a lot table, and i would like to insert each line 
> from each lot in a table, containing the id of the lot.
>
> I've tried: SELECT gid, St_boundary(the_geom) INTO lines from lots and 
> postgis gave me an error:
>
> *NOTICE:  IllegalArgumentException: Number of points must be 0 or >3
> ERROR:  POSTGIS2GEOS conversion failed
>
> ********** Erro **********
>
> ERROR: POSTGIS2GEOS conversion failed
> SQL state: XX000*
>
> I'm wondering if that is the right approach? I'm not even sure if 
> boundary is what i am looking for. Can anyone help me? Why postgis 
> gave me this error?
>
> Thanks in advanced.
>
> George
>
>
> -- 
> George R. C. Silva
> Sigma Consultoria
>
> Desenvolvimento em GIS
> www.consultoriasigma.com.br <http://www.consultoriasigma.com.br>
> www.sigmaconsultoria.blogspot.com 
> <http://www.sigmaconsultoria.blogspot.com>
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