Hi Marcin,
thanks for your reply. I don't think, that will provide the results I am
looking for. I am deliberately aggregating all intersecting lines with
ST_Union because otherwise the query would result in several collections
per polygon, each collection containig the st_split result for one of
the intersecting lines (blades). But I want the polygon cut with all blades.
Currently I am trying Marcone's suggestion (although I cannot imagine
why this should solve anything - but you never know until you try, right?).
So, thank you both, Marcin and Marcone!
Regards,
Birgit
Am 15.06.2016 um 09:24 schrieb Marcin Mionskowski:
On Tue, 14 Jun 2016 15:37:40 +0200, Marcone <marconepe...@gmail.com>
wrote:
2016-06-14 9:52 GMT-03:00 Birgit Laggner <birgit.lagg...@thuenen.de>:
I would like to use the ST_Split function to split polygons from one
table with all intersecting lines from another table. Unfortunately,
I get the following error:
ERROR: Splitting a Polygon by a MultiLineString is unsupported
SQL Status:XX000
This is my query:
select betr_id, (cut).path[1], (cut).geom from (select betr_id,
st_dump(st_split) as cut from (select a.betr_id, ST_Split(a.geom,
st_union(b.geom)) from p_sam.nihb_2013_convex_hull_betr a left join
p_sam.ni_dlm13_aaa_gew_sie_ver_l b on st_intersects(a.geom, b.geom)
group by a.betr_id, a.geom) sel1) sel2;
The Manual contains the following info regarding this problem:
"The function supports splitting a line by (multi)point,
(multi)line
or (multi)polygon boundary, a (multi)polygon by line."
This might mean that I would be able to split a line by
multilinestrings, but a polygon only by single linestrings - is that
correct? Does anyone has a suggestion how I could work around this
problem (aside from looping the ST_Split with some function, DO
block or pgScript after selecting all intersecting linestrings per
polygon)?
Thanks a lot for any helpful suggestions!
I'm not sure if I understand your problem, but try use
ST_Split(st_multi(a.geom),
st_union(b.geom)). I'm not test this, but I think that will solve
your problem.
Best regards.
Have you tried to ST_Dump multilinestrings first?
Using CTE this could look like:
with
a as ( --polygon
select ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) a
),
b as ( --multilinestring
select ST_Union(
(select ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190,
190))),
(select ST_MakeLine(ST_MakePoint(191, 191),ST_MakePoint(200,
200)))
) b
),
c as ( --multilinestring dump -> 2 separate linestrings
select (ST_Dump(b)).geom c
from b
)
SELECT ST_AsText(ST_Split(a, c))
from a,c
where ST_Intersects(a,c)
Intersection check is done here on line parts.
Regards
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