[fdo-users] Issue getting spatial extent of DGN files

[Traian Stanev]

Hi,

If you are using the FDO OGR provider, this error message is expected as SpatialExtents aggregate is not natively implemented. This section of code probably explains the error message:

        //TODO: We need to add support for SpatialExtents() and Count()
        //in order to speed up initial connection to data in Map3D.
        //For now, this check will reject such requests and throw Map
        //into the slow way of getting the information -- a full table scan
        if (properties->GetCount() > 1)
            throw FdoCommandException::Create(L"Unsupported aggregate operation."); 

The workaround is to read all the features once and add their extents to get the overall extent -- at least, this is what is done in MapGuide and Map3D as workaround for providers that do not have SpatialExtents.

Also, consider creating an enhancement request in FDO Trac for this issue so that we can implement this functionality in the future.

Traian

________________________________________
From: fdo-users-bounces at lists.osgeo.org [fdo-users-bounces at lists.osgeo.org] on behalf of Elavazhagan. M [elavazhagan.mouniandy at kcubeconsulting.com]
Sent: Wednesday, January 05, 2011 5:34 AM
To: 'FDO Users Mail List'
Subject: [fdo-users] Issue getting spatial extent of DGN files

Hello List,

When I try to get spatial extent of a DGN feature class, I get the below exception:

“Unsupported aggregate operation.
   at OSGeo.FDO.Commands.Feature.ISelectAggregatesImp.Execute()”

This is the aggregate function I used:
ComputedIdentifier computedIdentifier = (ComputedIdentifier)Expression.Parse("(SpatialExtents(" + geometryColumnName + ") as spatial_extent)");

Can somebody please let me know if this is a known issue? If not, is there a workaround?

Thanks,
Ela.