[postgis-users] multiline to linestring

[Kevin Neufeld]

Hi Gus,

As noted from your error, ST_Dump() is a set returning function, ie. you 
need to perform something like 'select * from dump(...)'

Try this:
select geom from dump(
  (select linemerge(collect(the_geom)) from lines)
);

Cheers,
-- Kevin

Gustavo Ces wrote:
> Hi all,
>  
>        i´ve got a problem with ST_Dump() ( well, actually this one 
> doesn´t exist )
> and dump() function. I´m working with
>  
> "PostgreSQL 8.2.3 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 
> 3.4.2 (mingw-special)"
> "POSTGIS="1.2.1" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.5.0, 22 Oct 
> 2006" USE_STATS"
>  
> I want to convert linestrings from multilinestrings, with linemerge, 
> to obtain united linestrings in overlapping points
> with this sentence:
>  
> select dump(linemerge(collect(the_geom))) from lines
>  
> but i obtain:
>  
> ERROR: set-valued function called in context that cannot accept a set
> Estado SQL:0A000
> The result of:
>  
> select astext(LineMerge(Collect(the_geom))) from lines
>  
> is:
>
> "MULTILINESTRING((4.8938679245283 46.3443396226415,33.313679245283 
> 73.7028301886792,49.5872641509434 80.0707547169811,90.9583136792453 
> 89.2813679245283,54.3363797169811 103.03608490566,29.0620872641509 
> 103.293985849057,12.2125589622641 107.1625,11.1624233831055 
> 106.590266209164,10.4214805264064 107.529010012923,11.2220067193803 
> 108.417488521584,12.2326314413493 107.778056025276),(37.506947728971 
> 97.6302534161404,12.1756482134062 82.9892270906306))"
>  
> with numgeometries=2, the logic result with my original data.
> How can i extract those linestrings separately?
>  
> Gus
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