[Qgis-developer] Valid or invalid geom in PostGIS?

[A Huarte]

>From QGIS 2.14 the postgis server-side simplification uses the ST_RemoveRepeatedPoints method:
http://qgis.org/en/site/forusers/visualchangelog214/#feature-use-st-removerepeatedpoints-for-server-side-simplification-with-postgis-2-2-or-newer-layers

The tolerance depends of current map scale, but you could check results in postgreSQL for different tolerances: 1 ... 10 ...100.
To avoid invalid geometry errors, but simplifying data to maintain rendering performance, you can disable in QGIS the server-side simplification of that layer to only enable the local simplification (The original features are read from postgre and simplification runs when the geometry is rendered. This does not change the original feature).



      De: Mark Johnson <mj10777 at googlemail.com>
 Para: "qgis-developer at lists.osgeo.org" <qgis-developer at lists.osgeo.org> 
 Enviado: Martes 17 de enero de 2017 10:25
 Asunto: Re: [Qgis-developer] Valid or invalid geom in PostGIS?
   

let me be more clear: there are NO invalid geoms in the DB, as reported
by st_isvalid. what is strange:
* invalidities are reported in qgis log (this may be due to
simplification, thanks Alvaro)

Then attept an 'ST_Simplify(geom,tolerance)' on these geometries to see if these errors occur:- tolerance '1' seems to be the default value being used > 2017-01-16T11:34:52   1       NOTA: NOTICE:  Self-intersection at or near point
> 619746.32941695023 4869530.4882389866
> 2017-01-16T11:34:52   1       NOTA: NOTICE:  IllegalArgumentException: Invalid
> number of points in LinearRing found 3 - must be 0 or >= 4



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