[postgis-users] Contradiction between ST_IsValid() and ST_IsValidReason() ?

[Nicolas Ribot]

Hello

What is Postgis/geos version ?
Yes, one or two examples of these strange geometries would be nice.

Nicolas


On Wed, 23 Dec 2020 at 11:20, Andreas Neumann <andreas at qgis.org> wrote:

> Hi,
>
> I have the strange situation that ST_IsValid() claims a geometry is not
> valid, but then ST_IsValidReason() says 'Valid Geometry'
>
> Here is my query:
>
> SELECT
>     t_id,
>     ST_AsText(ST_MakeValid(geometrie)) AS geom_repaired,
>     ST_AsText(geometrie) AS geom_orig,
>     ST_IsValidReason(geometrie)
> FROM arp_npl.erschlssngsplnung_erschliessung_linienobjekt
>    WHERE ST_IsValid(geometrie) = False;
>
> And here parts of the output:
> [image: image.png]
>
> Why is this contradiction - and which one is right? ST_IsValid() or
> ST_IsValidReason() ?
>
> I had a quick look at the geometries in question and they are all
> LINESTRING geometries with a "loop". Visually it is not clear whether the
> LINESTRING is crossing itself or not.
>
> Any ideas? I could of course share these strange geometries.
>
> Thanks,
>
> Andreas
> --
> Andreas Neumann
> QGIS.ORG board member (treasurer)
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