[gdal-dev] Get WFS attributes form the gml namespace as OGR fields

[Even Rouault]

On jeudi 19 octobre 2017 23:56:29 CEST Tamas Szekeres wrote:
> It looks like DOWNLOAD_SCHEMA=NO would do the trick, but if I use this in a
> VRT file this way it crashes GDAL.

Just fixed the crash (related to the HTTP driver and GDAL_OF_SHARED open flag)

You can also prefix the URL with /vsicurl_streaming/ to avoid full ingestion 
into memory

> 
> <OGRVRTDataSource>
>     <OGRVRTLayer name="OKCounties">
>         <SrcDataSource>
> http://cstest.coordinatesolutions.com/geoserver/wfs?VERSION=1.1.0&REQUES
> T=GetFeature&TYPENAME=ogi:okcounties&SRSNAME=EPSG:900913
> </SrcDataSource>
>         <OpenOptions>
>             <OOI key="DOWNLOAD_SCHEMA">NO</OOI>
>         </OpenOptions>
>         <LayerSRS>EPSG:900913</LayerSRS>
>         <SrcSQL>SELECT *,
> 'BRUSH(fc:#00000000);PEN(c:#008000,w:3px);LABEL(f:"Arial",c:#008000,s:14px,t
> :{name})' as OGR_STYLE from "okcounties"</SrcSQL>
>     </OGRVRTLayer>
> </OGRVRTDataSource>
> 
> 2017-10-19 23:18 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
> > On jeudi 19 octobre 2017 22:55:50 CEST Tamas Szekeres wrote:
> > > Hi all,
> > > 
> > > It looks like whenever we have a dataset (shapefile,db table,etc...)
> > 
> > which
> > 
> > > has a
> > > column with such names like "description", "name", "location" GeoServer
> > > maps it to the elements in the gml namespace (in a 1.1 request),
> > > therefore DescribeFeatureType doesn't contain these attributes.
> > > 
> > > For example this response doesn't include the name attribute
> > > 
> > > http://cstest.coordinatesolutions.com/geoserver/wfs?VERSION=1.1.0&
> > 
> > SERVICE=WF
> > 
> > > S&REQUEST=DescribeFeatureType&TYPENAME=ogi:okcounties
> > > 
> > > However that attribute is returned in the GetFeature request in the
> > > gml:name section, like:
> > > 
> > > http://cstest.coordinatesolutions.com/geoserver/wfs?VERSION=1.1.0&
> > 
> > REQUEST=Ge
> > 
> > > tFeature&TYPENAME=ogi:okcounties
> > > 
> > > But as the result of this behaviour the WFS driver doesn't include this
> > > item in the layer definition. Is that possible to retrieve these
> > 
> > attributes
> > 
> > > from the WFS driver as OGR fields for example to use them in SQL
> > > expressions?
> > 
> > Hi Tamas,
> > 
> > If your need is to filter on the server, then you'll need to compose the
> > full
> > URL at hand.
> > If you want to post-filter, you can downloader the GetFeature request and
> > open
> > the GML file with the DOWNLOAD_SCHEMA=NO open option (or
> > GML_DOWNLOAD_WFS_SCHEMA=NO configuration option)
> > This will prevent the GML driver from trying to use the schema, and then
> > it
> > will discover the gml:name element.
> > 
> > OGRFeature(okcounties):155
> > 
> >   gml_id (String) = okcounties.155
> >   name (String) = BEAVER
> >   state (Integer) = 40
> >   county (Integer) = 7
> >   stateplane (String) = N
> >   MULTIPOLYGON (((-100.945566 ....)))
> > 
> > The XSD parser used by the WFS and GML drivers could also possibly be
> > modified
> > to hard-code the definition of those few GML fields (although they might
> > depend on the GML version).
> > 
> > 
> > Otherwise you can also use the GMLAS driver, but the result will be a bit
> > inconvenient to use as it will create a dedicated layer for the name
> > attribute
> > (as gml:name can be repeated):
> > 
> > $ ogrinfo GMLAS:out.xml
> > INFO: Open of `GMLAS:out.xml'
> > 
> >       using driver `GMLAS' successful.
> > 
> > 1: okcounties (Multi Surface)
> > 2: okcounties_metadataproperty (None)
> > 3: okcounties_name (None)
> > 4: location (None)
> > 
> > OGRFeature(okcounties):1
> > 
> >   ogr_pkid (String) = 213FC01A8AA5FA1E1ADC65B21904DA34_okcounties_1
> >   id (String) = okcounties.155
> >   state (Integer64) = 40
> >   county (Integer64) = 7
> >   stateplane (String) = N
> >   MULTIPOLYGON (((-100.945566....)))
> > 
> > OGRFeature(okcounties_name):1
> > 
> >   ogr_pkid (String) = 213FC01A8AA5FA1E1ADC65B21904DA34_okcounties_1_name_1
> >   parent_ogr_pkid (String) = 213FC01A8AA5FA1E1ADC65B21904DA34_okcounties_1
> >   value (String) = BEAVER
> > 
> > Even
> > 
> > 
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com


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