[Mapserver-dev] Re: OGR Layers

Frank Warmerdam warmerdam at pobox.com
Tue Sep 30 23:07:45 EDT 2003

Steve Lime wrote:
> Other drivers ALWAYS ignore FILTERITEM. There is no provision to default
> to the MapServer processor. I think that might get really confusing. 
> Could the MapServer OGR driver be made smarter so that OGR sources with
> SQL support (e.g. Oracle Spatial) behave like any other database driver
> while those that don't behave like shapefiles? I rather see a change
> like that than having to update all the other drivers for consistent
> behavior. Seems like that would be pretty easy to document and would be
> consistent with the way it works now. 


All OGR drivers support some form of SQL.  Basic ones support "OGR SQL"
interpreted within the driver.  Others pass it through to an underlying
database.  When you say other drivers ignored FILTERITEM, you mean all
drivers except OGR *and* shapefile, right?

I am not keen on having the OGR layer behaviour vary significantly based
on whether the underlying driver supports "native" SQL.  That would seem
to violate the idea of OGR driver abstraction.

We could add a PROCESSING option to control whether the FILTER is
interpreted as a WHERE statement, or a FILTERITEM based query.  Or
we could try to auto-detect it from the expression itself ... I suppose.

Best regards,

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    | Geospatial Programmer for Rent

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