[postgis-users] multiline to linestring

[Kevin Neufeld]

Hi Gus,
Glad to help!
Actually, it is documented, 
(http://postgis.refractions.net/docs/ch06.html#id2704158) though I agree 
it definitely could be clearer, i.e. with some examples.
Here are some more links/examples to PostgreSQL's set returning functions...
http://www.postgresql.org/docs/8.2/static/xfunc-sql.html
http://www.postgresql.org/docs/8.2/static/functions-srf.html

Hope this helps,
-- Kevin

Gustavo Ces wrote:
> thanks Kevin!
>
>    Now i understand which was the problem!
>    And you run faster, how to extract geometry from geometry_dump type 
> (?) was the next question! :)
>    It´s not documentated, so i supose it´s a composite type and you 
> know how to access it after search that type in database, don´t you?
>
>
>
> Gus
> ----- Original Message ----- From: "Kevin Neufeld" 
> <kneufeld at refractions.net>
> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
> Sent: Wednesday, February 06, 2008 5:22 PM
> Subject: Re: [postgis-users] multiline to linestring
>
>
>> 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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