[postgis-users] GEOSUnaryUnion: TopologyException: found non-noded intersection BUT geom is valid

Wed Sep 19 06:27:05 PDT 2018

Hi,

ср, 19 сент. 2018 г. в 12:52, Birgit Laggner <birgit.laggner at thuenen.de>:

> Dear Darafei,
>
> in preparation of filing the ticket, I tested the ST_Union on my selected,
> supposedly problematic geometries. Interestingly, the ST_Union worked
> without a problem on my small selection table. I aborted the ticket
> creation because I can't file this as a reproducible bug.
>

Things to consider:
 - ST_Union(geom, geom) and ST_Union([geom...]) are different code paths;
 - ST_Union([geom...]) may depend on order of the features;
 - These bugs are hard to fix as they are hard to reproduce when you're
looking at it.

Please file the bug/dataset even if you're not sure it is properly
reproducible.

>
> My (then unnecessarily complicated workaround) of course worked fine, too.
> That means, I am able to get my work done, unfortunately, I still don't
> know what the original problem was.
>
> I am willing to let it rest and mark it as mysterious behaviour of a large
> dataset, as long as nobody has a specific interest to go to the bottom of
> the problem?
>
> Thanks a lot again for the idea with the wrapper to extract to problematic
> rows.
>
> Kind regards,
> Birgit
>
> ------------------------------
> *Von: *"Birgit Laggner" <birgit.laggner at thuenen.de>
>
> *An: *"PostGIS Users Discussion" <postgis-users at lists.osgeo.org>
> *Gesendet: *Mittwoch, 19. September 2018 09:47:41
>
> *Betreff: *Re: [postgis-users] GEOSUnaryUnion: TopologyException: found
> non-noded intersection BUT geom is valid
>
> Dear Darafei,
>
> good idea to write a wrapper to ferret out the offending rows. I had to
> change it a bit because I don't use ST_Union(geometry, geometry) but the
> aggregate ST_Union(geometry).  Since I am not very experienced in writing
> aggregates, I modified the wrapper that it fits for ST_Union(geometry[])
> and used it in my query with ST_Union_Fails(array_agg(geom)).
>
> I have found 3 groups with a total of 923 geometries which returned an
> error with ST_Union.
>
> As soon as I get access to my old userID, I will file the them as a ticket.
>
> In the meantime I will try to union the problematic geometries in a loop
> one at a time with st_makevalid after each loop - maybe that will work as a
> workaround, now I could reduce the number of geometries dramatically.
>
>
> Thank you very much for your help!
>
> Kind regards,
> Birgit
>
>
>
> ------------------------------
> *Von: *"Darafei \"Komяpa\" Praliaskouski" <me at komzpa.net>
> *An: *"PostGIS Users Discussion" <postgis-users at lists.osgeo.org>
> *Gesendet: *Mittwoch, 19. September 2018 02:46:42
> *Betreff: *Re: [postgis-users] GEOSUnaryUnion: TopologyException: found
> non-noded intersection BUT geom is valid
>
> Hi,
> This is not supposed to happen.
>
> Can you please isolate the offending rows unioning them pairwise and file
> them as a ticket? Here's a handy helper function that returns True if Union
> failed:
>
> create or replace function st_union_fails(geom1 geometry, geom2 geometry)
>     returns boolean
> as $$
> begin
>     begin
>         geom1 = ST_Union(Geom1, geom2);
>         return false;
>         exception when others
>         then
>             return true;
>     end;
> end;
> $$
> language plpgsql;
>
>
>
>
> вт, 18 сент. 2018 г. в 16:25, Birgit Laggner <birgit.laggner at thuenen.de>:
>
>> Dear discussion group,
>>
>> I am trying to ST_Union several polygons and get a TopologyException
>> (GEOSUnaryUnion: TopologyException: found non-noded intersection  between
>> LINESTRING (3.56442e+06 5.42679e+06, 3.56442e+06 5.42679e+06) and
>> LINESTRING (3.56442e+06 5.42679e+06, 3.56442e+06 5.42679e+06) at
>> 3564420.7944701263 5426786.9800475985).
>> I have tested with ST_Valid and all polygons in the datasets are valid.
>>
>> The dataset is pretty large (53.5 Mio. polygons) and will probably get
>> grouped into around 8.7 Mio resulting geometries during ST_Union.
>>
>> If I try to ST_Union the geometries near the point ST_Union mentions in
>> the error message (ST_Buffer with up to 100 metres), everything works fine.
>> I am out of ideas how to find the problematic geometry or at least how to
>> work around the TopologyException.
>>
>> My PostGIS version is: "POSTGIS="2.3.3 r15473" GEOS="3.5.1-CAPI-1.9.1
>> r4246" SFCGAL="1.2.2" PROJ="Rel. 4.9.2, 08 September 2015" GDAL="GDAL
>> 1.11.3, released 2015/09/16" LIBXML="2.9.3" LIBJSON="0.11.99" TOPOLOGY
>> RASTER"
>>
>>
>> I would be very glad if anyone would come up with ideas how to solve my
>> problem.
>>
>> Thanks a lot in advance!
>>
>> Regards,
>> Birgit
>>
>>
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>>
> --
> Darafei Praliaskouski
> Support me: http://patreon.com/komzpa
>
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-- 
Darafei Praliaskouski
Support me: http://patreon.com/komzpa
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