[postgis-users] Getting TopologyExections when trying to node linestrings to create an overlay

[Rémi Cura]

Hey Sandro,
this is a precision related issue,
coordinates are way too big and should be translated.
Cheers,
Rémi-C

2015-02-09 12:25 GMT+01:00 Sandro Santilli <strk at keybit.net>:

> On Tue, Feb 03, 2015 at 11:28:35AM -0500, BladeOfLight16 wrote:
>
> >
> https://drive.google.com/file/d/0B_6I7kRgE8teVUpha2Q4ZlNDMWs/view?usp=sharing
> .
>
> ...
>
> > DO $$
> > DECLARE problem_row error_generating_polygons%ROWTYPE;
> > BEGIN
> >   FOR problem_row IN (SELECT * FROM error_generating_polygons) LOOP
> >     BEGIN
> >       PERFORM ST_Union(ST_Boundary(geom))
> >       FROM UNNEST(problem_row.polygons) p (geom);
> >       RAISE NOTICE 'geom_set_id % succeeded', problem_row.geom_set_id;
> >     EXCEPTION
> >       WHEN OTHERS THEN
> >         RAISE NOTICE 'Error for geom_set_id % (Code %): %',
> > problem_row.geom_set_id, SQLSTATE, SQLERRM;
> >     END;
> >   END LOOP;
> > END
> > $$;
>
> First of all I confirm it still happens with GEOS="3.5.0dev-CAPI-1.9.0
> r4038".
> Second, I took a look at a random set (geom_set_id=1) and I found it pretty
> big. That's to say you could probably further reduce the dataset for the
> ticket. That set contains 109 polygons, I can get the error by attempting
> to union the boundaries of the first 40 in that set, and I'm sure you can
> further reduce the input.
>
> So my suggestion:
>
>  1) file the ticket
>  2) attach the _smallest_ input that reproduces the problem
>
> About ST_IsValid: lines are always valid, so there's no need to test.
> Most likely this is a robustness issue failing to deal with very close
> but not equal lines.
>
> NOTE: I've tried my reduced input (~40) geoms against the topology builder
> and it also resulted in errors, until I specified a tolerance of 1e-4.
>
> --strk;
>
>   ()   Free GIS & Flash consultant/developer
>   /\   http://strk.keybit.net/services.html
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