[postgis-devel] [PostGIS] #878: ST_LineMerge with collection
PostGIS
trac at osgeo.org
Mon Mar 21 07:53:23 PDT 2011
#878: ST_LineMerge with collection
---------------------+------------------------------------------------------
Reporter: strk | Owner: pramsey
Type: defect | Status: new
Priority: medium | Milestone: PostGIS 2.0.0
Component: postgis | Version: trunk
Keywords: |
---------------------+------------------------------------------------------
According to GEOS dox about LineMerger:
* Any dimension of Geometry is handled.
* The constituent linework is extracted to form the edges.
According to PostGIS manual:
{{{
Only use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or
geometry collection into this function, it will return an empty
GEOMETRYCOLLECTION
}}}
Reality:
{{{
SELECT ST_AsText(ST_LineMerge(
'GEOMETRYCOLLECTION(
MULTILINESTRING(
(1656318.45 4833344.45,1656321.79 4833339.62,1656312.54 4833333.49),
(1656312.54 4833333.49,1656309.68 4833337.07)
),
LINESTRING(1656309.68 4833337.07,1656318.45 4833344.45)
)'));
st_astext
---------------------------------------------------------
LINESTRING(1656309.68 4833337.07,1656318.45 4833344.45)
(1 row)
}}}
Basically, the MULTILINESTRING part was simply _discarded_.
Works fine if the input is transformed in a MULTILINESTRING
(without the collection).
I'm not sure if the bug is in postgis or geos, will check.
Surely dox of postgis and geos disagree on the matter.
--
Ticket URL: <http://trac.osgeo.org/postgis/ticket/878>
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