[gdal-dev] Question about command line options -append

[Victor Chernetsky]

Thanks, this helps!

The thing is I cannot really use layer name to identify an AmigoCloud
dataset. In AmigoCloud we have names, but they are not guarantied to be
unique. We use dataset Id to identify a dataset (ogr layer) instead. In my
example "Visits" it's just a name of the source data file, which gdal uses
as a layer name. This is fine, but for destination AmigoCloud dataset I
specify a dataset id explicitly anyway. So I know my destination dataset,
and if it exists or not. I think with the info I have now I could do few
small changes to handle these cases.



*Victor Chernetsky*


+1 (408) 368-4607
victor at amigocloud.com

On Tue, Nov 28, 2017 at 4:01 PM, Even Rouault <even.rouault at spatialys.com>
wrote:

> On mardi 28 novembre 2017 15:40:46 CET Victor Chernetsky wrote:
>
> > Here is my example:
>
> > ogr2ogr -overwrite -f AmigoCloud "AmigoCloud:15276 datasets=100056"
>
> > ~/Downloads/Visits.geojson
>
> >
>
> > I am trying to append, or overwrite data into existing dataset id:100056.
>
> > But it still created a new dataset, and it did not delete/clean old
>
> > dataset.
>
>
>
> -overwrite overwrite *layers* not datasets
>
> Here it will probably create a new layer because the layer name of
> Visits.geojson
>
> must be "Visits" and probably doesn't exist yet in your dataset.
>
>
>
> If you want to overwrite an existing layer foo with the geojson, you must
> add "-nln foo"
>
>
>
> > I am thinking I need to do something in
>
> > my OGRAmigoCloudDataSource::ICreateLayer(). I am not checking if dataset
>
> > exist. I always create a new one.
>
>
>
> You can have a look at the ogr2ogr logic to decide how to overwrite a
> layer:
>
> https://github.com/OSGeo/gdal/blob/trunk/gdal/apps/ogr2ogr_lib.cpp#L3180
>
>
>
> For non-ogr2ogr clients, you could indeed add a check if a layer of same
> name already exists
>
> A number of drivers also support a OVERWRITE=YES layer creation option
>
> See
>
> https://github.com/OSGeo/gdal/blob/trunk/gdal/ogr/ogrsf_frmts/carto/
> ogrcartodatasource.cpp#L412
>
>
>
> The advantage when you write an example is that you have tens of examples
> to get inspiration from ;-)
>
>
>
> Even
>
>
>
> --
>
> Spatialys - Geospatial professional services
>
> http://www.spatialys.com
>
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