Strange OGR VRT Issue

[Frank Warmerdam]

Pascoe,Tim [Burlington] wrote:
> I'm experimenting with placing my OVF file in line, in order to pass in 
> some variables for a custom WHERE Statement. The first step I took was 
> changing my OVF file to use the scrSQL tag with a very simple SQL 
> statement, instead of the srcLayer tag. Both OVF files point to the same 
> view, in the same database.
> 
> New File:
> <OGRVRTDataSource>
>     <OGRVRTLayer name="CABINPoints">
>         <SrcDataSource>ODBC:****/****@CABIN</SrcDataSource>
>         <SrcSQL>SELECT * FROM OGRPoints</SrcSQL>
>           <FID>sitedetailsid</FID>
>         <GeometryType>wkbPoint</GeometryType>
>         <LayerSRS>WGS84</LayerSRS>
>     <GeometryField encoding="PointFromColumns" x="longitude" y="latitude"/>
>     </OGRVRTLayer>
> </OGRVRTDataSource>
> 
> Old FIle:
> <OGRVRTDataSource>
>     <OGRVRTLayer name="CABINPoints">
>         <SrcDataSource>ODBC:****/****@CABIN,OGRPoints</SrcDataSource>
>         <SrcLayer>OGRPoints</SrcLayer>
>           <FID>sitedetailsid</FID>
>         <GeometryType>wkbPoint</GeometryType>
>         <LayerSRS>WGS84</LayerSRS>
>     <GeometryField encoding="PointFromColumns" x="longitude" y="latitude"/>
>     </OGRVRTLayer>
> </OGRVRTDataSource>
> 
> The problem is, the old OVF returns a proper image, while the new one 
> returns a blank image. I ran the new file through OGRInfo and shp2ogr, 
> and both behave properly.
> 
> So……..why am I getting a blank image with the scrSQL tag? I'm using the 
> latest version of the MS4W file set, but running on IIS on Windows 2000. 
> Any suggestions would be great - it's probably somthing very simple I'm 
> missing :)

Tim,

I see no obvious reason it wouldn't work.  Do you mean shp2img when
you say shp2ogr?  If it works with shp2img at the commandline, but not
with mapserv then I would suspect some sort of subtle permissions
problem but it seems hard to understand why.

You might want to include the layer name in the SrcDataSource in the
"new" case otherwise OGR will try to collect info on all the tables
which may be slow, and perhaps is even contributing to the problem.

Best regards,
-- 
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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 OSGeo, http://osgeo.org