On Wed, Nov 15, 2017 at 3:49 PM, Markus Metz <[email protected]> wrote: > On Wed, Nov 15, 2017 at 1:36 PM, Helmut Kudrnovsky <[email protected]> wrote: >> >> Background of the question in subject: the GRASS algs in upcoming QGIS3 >> are working with v.external linked data. >> >> I've seen some modules doesn't work with such kind of data. >> >> Is there maybe a list already available? > > It depends also on the format that is linked in with v.external. For all > formats that do not have a key column (e.g. shapefile), attributes are not > accessible, and attributes would get lost when modifying the > geometries.Therefore it is generally not safe to link vector data with > v.external. In many cases it does not make sense to use v.external linked > data with simple features, instead vector data should be imported to get > true topology. If upcoming QGIS3 is working with v.external linked data, the > GRASS interface of QGIS is effectively broken.
I have turned this into a potential new snippet for the v.external manual: ----- snip ----- Due to these data model differences <em>v.external</em> does not work with all data formats. In general, for all formats that do not have a key column (e.g. SHAPE file), attributes are not accessible, and attributes would get lost when modifying the geometries. Therefore it is generally not safe to link vector data with <em>v.external</em>. In many cases it does not make sense to use <em>v.external</em> linked data with simple features, instead vector data should be imported with <em>v.import</em> or <em>v.in.ogr</em> to get true topology support. Importantly, point cloud data which do not have topology, can be linked with <em>v.external</em>. ----- snap ----- Please review. Markus _______________________________________________ grass-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-dev
