[postgis-users] Problems with GeomUnion

[Bill Binko]

On Fri, 8 Apr 2005, Mark Cave-Ayland wrote:

> > I had tried your query before, and it returned zero rows (which makes 
> > sense given the constraint). The buffer() seemed to be 
> > converting them to 
> > non-2d.
> 
> Right, I see now. What does the following SQL give you (it you should give
> you the number of dimensions for buffer(parcel_shape, 0) for all valid
> geometries where the dimension is not equal to 2):
> 
> SELECT foo.oid, ndims(buffer(foo.parcel_shape, 0)) FROM (SELECT oid,
> parcel_shape FROM parcels WHERE isvalid(parcel_shape) = 't') AS foo WHERE
> ndims(buffer(foo.parcel_shape, 0)) != 2
> 
After many NOTICE's, it returns zero rows.

> 
> This is beginning to get out of my knowledge area - have you seen the
> earlier post about using JUMP to validate features?
> 

I have, but am hoping to avoid that if I can fix it within PostGIS.  
Mainly because this data is on a headless server and I'd have to move it 
to get a GUI to hit it.

Bill