Hi Nicolas,
Thanks again.
Well, this working, but this not performant...
Based on your suggestion, I tried this:
in view1:
ST_Multi(ST_LineMerge(ST_Union(wkb_geometry)))::geometry(MultiLineString,21781)
AS wkb_geometry
Then in view2:
ST_CollectionHomogenize(wkb_geometry)::geometry(LineString,21781) AS
wkb_geometry
FROM view1
WHERE ST_NumGeometries(wkb_geometry) = 1;
And I can detect problems by doing:
SELECT id FROM view1 WHERE ST_NumGeometries(wkb_geometry) != 1;
But this is slowing down a lot.
I think that the ST_CollectionHomogenize is not the right way. Is there
a better function to transform multiline to line if I am sure I only
have lines?
Greetings,
Denis
On 03/27/2012 02:29 PM, Nicolas Ribot wrote:
On 27 March 2012 08:02, Denis Rouzaud<denis.rouz...@gmail.com> wrote:
Hi Nicolas, hi all,
Thanks for your reply.
The problem is:
- I cannot filter my view using where geometryType(wkb_geometry) =
'LINESTRING' as it will still return the same error
- I cannot check the result of ST_LineMerge in the where clause since
aggragates are not allowed in wheres
- If I cast to a MULTI, I don't how to check that it is castable to a
LineString.
So, I'll try to reformulate:
- Can I check if a MultiLineString is in fact a LineString ?
- Is there a way to test the result of LineMerge to see if it is a
LineString or MultiLineString?
Hi,
The number of elements in the collection will tell you if it is a
linestring (1 element): st_numGeometries(), or the geometry type
(geometryType() ) will start by 'MULTI' in case of collection.
You could add a rule on your view to disallow st_lineMerge results
producing MULTI elements.
Nicolas
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