[gdal-dev] GDAL overrite file error

[Even Rouault]

Le jeudi 07 mai 2015 20:27:03, Stefan Keller a écrit :
> Hi,
> 
> Regarding overwrite:
> I think the "-overwrite" parameter in ogr2ogr commandline tool does not
> work. I tried it with drivers like "ESRI Shapefile", GeoJSON and others
> without success.
> ogr2ogr always exits and reports
> "ERROR 6: The GeoJSON driver does not overwrite existing files."
> Why should drivers not be able to overwrite?

-overwrite causes an existing layer to be deleted before being recreated, for 
drivers that support the DeleteLayer() API.
It does not cause an existing dataset to be destroyed however (which would be 
calling DeleteDataSource(), which isn't implemented by all drivers either), 
which is the issue you must have with the geojson driver.
For shapefiles, that works in my testing however.
I know this is a bit user unfriendly: nothing fundamentally impossible to 
improve here, just historic behaviour.

> Is'nt deleting files common task for all drivers (meaning to be
> handled outside the actual writer drivers)?

Implementation of DeleteLayer() is driver specific code, since only drivers 
know which files (when files are involve. Think to a PostGIS table) are related 
to a layer.

> 
> -S.
> 
> 2015-02-06 11:06 GMT+01:00 Even Rouault <even.rouault at spatialys.com>:
> > Le vendredi 06 février 2015 10:42:04, Carlos Piury a écrit :
> >> Hi, I am trying to create a vector format (i.e. ESRI Shapefile) from
> >> laser file (.las), and it works fine, but when I try to overwrite the
> >> file I get the following error:
> >> 
> >> ERROR 1: Layer 'output' already exists
> > 
> > --> The message is hopefully clear enough and comes from the
> > implementation of CreateLayer() in the shape file driver. You have to
> > destroy the files of the shapefile first if they exists. You can use
> > DeleteDataSource() for that.
> > 
> >> terminate called after throwing an instance of 'std::runtime_error'
> >> 
> >>   what():  output layer creation failed
> >> 
> >> Aborted (core dumped)
> > 
> > Does this come from inside GDAL code or you own code ? Looks like from
> > yours, if you transform GDAL errors into C++ exceptions.
> > 
> >> I am using the next code to create the layer:
> >> 
> >> OGRSFDriverH formatTranslateDriver =
> >> OGRGetDriverByName(argFormat->sval[0]);
> >> 
> >> OGRDataSourceH dataset = OGR_Dr_CreateDataSource(formatTranslateDriver,
> >> argOutput->sval[0], 0);
> >> 
> >> OGRLayerH layer = OGR_DS_CreateLayer(dataset, layerName.c_str(), 0,
> >> wkbPoint25D, 0);
> >> 
> >> Any idea about this error?
> >> 
> >> Thanks.
> > 
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