[postgis-users] st_split

[franco base]

Thanks Remi.
I test your function on my example
and I have the same problem with ST_Split.

Maybe some is wrong in geometry,
but I don't understand where is the error.


2013/10/28 Rémi Cura <remi.cura at gmail.com>

> Hey, you may want to use a function I wrote as a wrapper around ST_Split
> to allow splitting a (multi-)line with (multi) points.
>
> Here it is.
> It still thinks it should be somewhere is the core.
>
> Cheers,
>
> Rémi-C
>
> --creating a simple wrapper around ST_Split to allow splitting line by
> multipoints
>  DROP FUNCTION IF EXISTS public.Split_multi(input_geom geometry ,blade
> geometry);
>  CREATE FUNCTION public.Split_multi(input_geom geometry ,blade geometry)
>   RETURNS geometry AS
>  $BODY$
> --this function is a wrapper around the function ST_Split to allow
> splitting mutli_lines with multi_points
>  --
>     DECLARE
>  result geometry;
> simple_blade geometry;
>  blade_geometry_type text := GeometryType(blade); geom_geometry_type text
> := GeometryType(input_geom);
>  blade_coded_type SMALLINT; geom_coded_type SMALLINT;
>      BEGIN
>
> --finding type of input : mixed type are not allowed
>  --if type is not multi, simply splitting and returning result
>
> IF blade_geometry_type NOT ILIKE 'MULTI%' THEN
>  --RAISE NOTICE 'input geom is simple, doing regular split';
> RETURN ST_Split(input_geom,blade);
>  ELSIF blade_geometry_type ILIKE '%POINT' THEN
>  blade_coded_type:= 1;
> ELSIF blade_geometry_type ILIKE '%LINESTRING' THEN
>  blade_coded_type:= 2;
> ELSIF blade_geometry_type ILIKE '%POLYGON' THEN
>  blade_coded_type:= 3;
> ELSE
>  RAISE NOTICE 'mutliple input geometry types for the blade : should be
> homogenous ';
>  RETURN NULL;
> END IF;
>
> IF geom_geometry_type ILIKE '%POINT' THEN
>  geom_coded_type:= 1;
> ELSIF geom_geometry_type ILIKE '%LINESTRING' THEN
>  geom_coded_type:= 2;
> ELSIF geom_geometry_type ILIKE '%POLYGON' THEN
>  geom_coded_type:= 3;
> ELSE
>  RAISE NOTICE 'mutliple input geometry types for the geom: should be
> homogenous ';
>  RETURN NULL;
> END IF;
>
> result := input_geom;
>  --Loop on all the geometry in the blade
> FOR simple_blade IN SELECT (ST_Dump(ST_CollectionExtract(blade,
> blade_coded_type))).geom
>  LOOP
> result:=
> ST_CollectionExtract(ST_Split(result,simple_blade),geom_coded_type);
>  END LOOP;
> RETURN result;
>      END;
> $BODY$
>  LANGUAGE plpgsql IMMUTABLE;
>  ----
> --Testing the function
>  SELECT ST_AsText(Split_multi(geom, blade))
> FROM (
>  SELECT ST_GeomFromText('Multilinestring((-3 0, 3 0),(-1 0,1 0))') AS
> geom,
>  ST_GeomFromText('MULTIPOINT((-0.5 0),(0.5 0))') AS blade
> --ST_GeomFromText('POINT(-0.5 0)') AS blade
>  --ST_GeomFromText('MULTILINESTRING((0 1, 0 -1),(0 2,0 -2))') AS blade
>  --ST_GeomFromText('MULTIPOLYGON(((0 1,0 -1 ,1 -1,0 1)),((0 2,0 -2,1 -2,0
> 2)))') AS blade
>  ) AS toto
>
>
> 2013/10/28 franco base <frenk.calza at gmail.com>
>
>> Hi.
>> I have a set of linestring and point on linestring.
>> I want cut the linestring on the point.
>> I can have n points for one linestring,
>> so I use ST_Split
>> (insted of ST_Line_Interpolate_Point and ST_Line_Substring)
>> but it doesn't work.
>>
>> line;geom_line;point;geom_point
>>
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11764;"0101000020BB0B00005713362F611F37410D996234AF335341"
>>
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11769;"0101000020BB0B00005EF0DD584620374139BF2762BC335341"
>>
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11762;"0101000020BB0B0000A5CBC785841F374156A2A33CB1335341"
>>
>> ST_GeometryType(St_Split(geom_line, geom_point))
>> give "ST_GeometryCollection"
>>
>> but
>>
>> (ST_Dump(ST_Split(geom_line, geom_point))).geom
>>
>> return only 3 linestring (one for record) and the geometry is egual to
>> geom_line
>>
>>
>> thanks.
>>
>> fb
>>
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>
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