[gdal-dev] ogr2ogr with append fails to convert truncated fields

[Even Rouault]

Le lundi 25 février 2013 16:57:08, Tamas Szekeres a écrit :
> Hi All,
> 
> Related to issue #3247 <http://trac.osgeo.org/gdal/ticket/3247> we
> experienced, that if we use ogr2ogr to append source data to a shapefile
> destination (by using the -append flag) and field name truncation is taking
> place, the corresponding values are not copied.
> 
> This is because when setting up the field index map (in ogr2ogr) the
> destination (truncated) field indexes are searched by the name of of the
> source fields (the long names).
> 
> Since it's not always trivial to find the correct fields by names, how
> about exposing the field map itself as an option, something like:
> 
> ogr2ogr -append -f "ESRI Shapefile" -fieldmap "0,1,2,3,4,5" destination.shp
>  [source]
> 
> 
> Would that workaround be sufficient?

That would certainly work, although not particularly user friendly, but 
shapefiles are not that user friendly with their various limitations.

Perhaps you could just work with spatialite DBs as intermediate and convert to 
shapefile at the end if it is really needed ?

A potential alternative to -fieldmap would be to have :

class OGRLayer:
{
   public:
          virtual int GetFieldIndex(const char* pszFieldname);
}

int OGRLayer::GetFieldIndex(const char* pszFieldname)
{
	return GetLayerDefn()->GetFieldIndex(pszFieldname);
}

int OGRShapeLayer::GetFieldIndex(const char* pszFieldname)
{
        int idx = OGRLayer::GetFieldIndex(pszFieldname);
        if( idx >= 0 )
                return idx;
        /* otherwise implement here truncation logic to find best match */
        /* caution: if there are several potential matches (for example 
verylongcolumnname1 being truncated to verylongna and verylongcolumnname2 
truncated to verylong~1) and you are looking for verylongcolumnXXX then return 
-1 */
}

> 
> 
> Best regards,
> 
> Tamas