[gdal-dev] Missing geometry type when using ogr2ogr to write FileGDB

[Jukka Rahkonen]

Even Rouault <even.rouault <at> mines-paris.org> writes:


> 
> Yes, when examining the
> 
>
"http://maps.zh.ch/wfs/FnsNSWFS?TYPENAME=svo_zonen&SERVICE=WFS&VERSION=1.1.0&REQUEST=DescribeFeatureType"

> you can see :
> 
>           <element name="msGeometry" type="gml:GeometryPropertyType" 
> minOccurs="0" maxOccurs="1"/>
> 
> So the geometry type is undefined. OGR then reports a unknown geometry type. 
> There could be a mix of geometries in such a layer.

Just for information, it is not uncommon that WFS servers advertise a
general geometry type "gml:GeometryPropertyType" even the layer contains
only one geometry type and therefore WFS clients should be aware of this.
General geometry type comes more or less automatically when setting up a WFS
service on top of Oracle because by default Oracle can hold any geometries
in the geometry column. It is possible to set a geometry type constraint
when creating a spatial index but it is not important for Oracle and
therefore the constraint is often missing. Even if it exists it is a bit
complicated to query. For example Geoserver knows how to do this check but
GDAL OCI driver does not. If someone gets interested in improving the OCI
driver, here is a basic part of the query.

select idxmeta.sdo_layer_gtype from all_sdo_index_info idxinfo,
all_sdo_index_metadata idxmeta
where idxinfo.index_name=idxmeta.sdo_index_name
and idxinfo.table_name='TABLE_NAME'

If WFS client cannot handle mixed geometry types on one layer then it could
perhaps take the first not empty geometry from the WFS response and initiate
the layer to use that geometry type. To be on a safe side it might create a
multipolygon or multilinestring layer even if the first feature is simple.
Another geometry type appearing later in the data will lead to an error but
it cannot be avoided anyway if client cannot handle mixed layers.

-Jukka Rahkonen-