[GRASS-user] Import gpkg point map

[Markus Metz]

On Thu, Jun 27, 2019 at 7:37 AM Micha Silver <tsvibar at gmail.com> wrote:
>
>
> On 26/06/2019 23:44, Markus Metz wrote:
>
>
>
> On Wed, Jun 26, 2019 at 10:16 PM Micha Silver <tsvibar at gmail.com> wrote:
> >
> >
> >
> >
> >
> > micha at TP480:code$ ogrinfo -so ../GIS/Ashalim/ashalim_train_pts.gpkg
> > INFO: Open of `../GIS/Ashalim/ashalim_train_pts.gpkg'
> >       using driver `GPKG' successful.
> > 1: ashalim_train_pts (Point)
> > 2: layer_styles (None)
> >
> >
> > The style ??!!
> >
> >
> > I removed that "layer_styles" table from the gpkg db, and deleted the
entry from gpkg_contents, and now the import works.
> >
> > Who would have guessed ?
> >
> > I suppose that I should have specified the layer in v.import to avoid
this problem.
>
> Yes, specifying the layer should work.
>
> I have seen this layer_styles layer before in other GPKG files but don't
know what this is good for. GDAL documentation at
> https://gdal.org/drivers/vector/gpkg.html
> does not mention any style information.
>
>
> It comes from QGIS, where you can save a default layer styling directly
into the gpkg. Very convenient, but I never thought it would appear to
GRASS as a second layer without geometry or CRS.

This is not GRASS, it is OGR that recognizes it as a separate layer without
geometry or CRS. I guess ogr2ogr skips this layer because there are no
geometries in it.

In theory, v.in.ogr could skip empty OGR layers, but in practice it is not
always easy to get the feature count of a layer, it depends on the data
format. Sometimes, e.g. for OSM pbf, you need to read the whole OGR
datasource to figure out the number of features per layer.

In v.in.ogr, there are already a number of special cases for specific
OGR-supported formats, and I would like to keep these format-specific
treatments to a minimum, avoiding yet another special case for GPKG + empty
layer. Ideally, the GPKG driver of OGR would not expose such empty or
special layers.

Markus M
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