Problem with Mapserver Virtual Spatial Data (ogr)

Thu May 18 23:42:26 PDT 2006

OGR tries to automatically detect the primary key of a table. This does not
always work automatically. The reason could be for instance the data type
used for your primary key, or maybe a small flaw in the driver's code.
Another example, using ODBC on Access, there is trouble detecting the
primary key because of a not implemented ODBC function in the Microsoft
driver. 

Best regards,
Bart

-----Oorspronkelijk bericht-----
Van: UMN MapServer Users List
[mailto:MAPSERVER-USERS at LISTS.UMN.EDU]Namens Christian Wilmes
Verzonden: vrijdag 19 mei 2006 8:40
Aan: MAPSERVER-USERS at LISTS.UMN.EDU
Onderwerp: Re: [UMN_MAPSERVER-USERS] Problem with Mapserver Virtual
Spatial Data (ogr)

Hi Frank,

thank you very much for your help!

With the line
CONFIG "PGSQL_OGR_FID" "fieldname" 
in the Map section everything works very well.

But now I've still got one more question, just an understanding one. I've
got testet the "Virtual Spatial Data" with a MySQL Database a few days ago
and there everything works well without a line like that. Where could be the
reason?

Best Regards
Christian

-------- Original-Nachricht --------
Betreff: Re: [UMN_MAPSERVER-USERS] Problem with Mapserver Virtual Spatial
Data (ogr)
Datum: Thu, 18 May 2006 16:55:40 -0400
Von: Frank Warmerdam <warmerdam at POBOX.COM>
An: MAPSERVER-USERS at LISTS.UMN.EDU

> 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

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