Problem with Mapserver Virtual Spatial Data (ogr)

[Frank Warmerdam]

Christian Wilmes wrote:
> Hello,
> 
> first of all sorry for cross posting, but I've got no idea where I have to
> search the mistake so I post it to the GDAL and the Mapserver Mailinglist.
> 
> I'm trying to publish a WFS-Server. The Data (only Point-Data) are in a
> PostgreSQL-Database (no PostGIS!). So the connection to the data is over
> "Virtual Spatial Data". The getCapabilities and DescribeFeatureType request
> both work very well. Only the GML-Document getting with the getFeature
> request is not correct. The number of features in the GML-Document are
> correct too every time, but the features are not in the Bounding Box. The
> features in the GML-Document are always the feature which are on the top of
> the table they come from. Only the number of feature is correct. The MBR
> (Minimum Boundig Rectangle) on the top of the GML-Document amasingly the
> correct one. So it don't fit to the features in the document. Testing the
> connection with "ogrinfo" and a Boundig-Box is working correct. If I'm
> trying to make a WMS-Server with the same Data and the same OGR-file it
> works very well.

Christian,

I believe the problem is that OGR is not successfully identifying a column
in the table to use as a "feature id".  For WFS queries the results are
fetched in two passes for various historical reasons.  The first pass
results in a fetch of the feature ids of the features, and the second
pass fetches features by id.  Unfortunately, if OGR cannot select a good
unique feature id column, then it assigns them serially.  The first pass
has the spatial query "in place" so the resulting fids are 1, 2, 3, etc.
But the second pass does not have the spatial filter in place, so it ends
up returning the wrong features.

Ideally you would ensure you have a single integer column setup as a
primary index for your postgres table.  If that is the case it *should*
get used as the fid.

If not, you may be able to include the following line in your MAP file
(in the MAP section, not the layer):

   CONFIG "PGSQL_OGR_FID=fieldname"

to indicate what fieldname should get used as FID.  This should be
available with GDAL/OGR 1.3.2.

PS. the much talked about one-pass-query would resolve this problem.

Good luck,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGF, http://osgeo.org