[Qgis-user] Dissolve tool failing to produce outputs

[Andrew Harfoot]

I'm seeing very strange behaviour with a particular shapefile in QGIS 
3.4.1. The data can be obtained here:

https://drive.google.com/file/d/1BPVnsUbJREYh6TvLM07GAzXMiMneHemN/view?usp=sharing

When I run the /Vector Geometry > Dissolve/ Processing tool on it, no 
errors are raised, an output layer is created containing one row with no 
geometry. This happens regardless of the Processing 'Invalid features 
filtering' setting.

Running the /GDAL > Vector geoprocessing > Dissolve/ tool on the data 
immediately returns an invalid geometry (self intersection) error, but 
running /Vector Geometry > Check validity/ finds no errors using either 
the GEOS or QGIS engine.

If the /Vector Geometry > Dissolve/ tool is run on a selection from the 
shapefile, it will complete successfully if all but one feature is 
selected, *regardless of which feature is left unselected*.

I'm not sure whether this is a bug, or my data. Does anyone have any 
explanation for the observed behaviour?

Cheers,

Andy

-- 
Andy Harfoot

GeoData Institute
University of Southampton
Southampton
SO17 1BJ

Tel:  +44 (0)23 8059 2719

www.geodata.soton.ac.uk

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