[postgis-users] Empty GeometryCollection and AsSVG

[strk at refractions.net]

On Wed, Oct 27, 2004 at 01:40:22PM +0200, Olivier Courtin wrote:
> Hi,
> 
> Still playing with AsSVG function, and i met a little problem, with
> query like :
> 
> SELECT AsSVG(simplify(the_geom, 1000), 1, 0) FROM my_table;
> 
> With some data and with a quite high simplify tolerance parameter, the
> simplify output could be empty. And become a GeometryCollection type...
> And this even if the original type was a Polygon or anything else...
> 
> And as AsSVG not handle rightly GeometryCollection type, output
> could be like that :
> 
> Row 1) M 572119 -1720173 l 1162 4085 -4360 -567 3198 -3518 
> Row 2) GEOMETRYCOLLECTION not yet supported
> Row 3) M 572119 -1720173 l -3198 3518 4360 567 -1162 -4085
> ...
> 
> 
> I provide below a partial patch for AsSvg who return an empty string if
> GeometryCollection is Empty.
> 
> So result will be :
> 
> Row 1) M 572119 -1720173 l 1162 4085 -4360 -567 3198 -3518 
> Row 2) 
> Row 3) M 572119 -1720173 l -3198 3518 4360 567 -1162 -4085
> ...
> 
> 
> Any better idea ?

What about a NULL ?
--strk;

> 
> 
> 
> diff -u against current cvs head :
> 
> --- lwgeom_svg.c        2004-10-27 13:13:12.000000000 +0200
> +++ patched_lwgeom_svg.c        2004-10-27 13:27:13.000000000 +0200
> @@ -92,8 +92,17 @@
>  
>         if (lwgeom_getType(geometry->type) == COLLECTIONTYPE)
>         {
> -               result = (char *)palloc(64); 
> -               sprintf(result, "GEOMETRYCOLLECTION not yet supported");
> +               inspected = lwgeom_inspect(SERIALIZED_FORM(geometry));
> +
> +               result = (char *)palloc(64);
> +
> +               if(inspected->ngeometries == 0){
> +                       sprintf(result, "%s", "");
> +               } else {
> +                       sprintf(result,
> +                               "GEOMETRYCOLLECTION not yet supported");
> +               }
> +
>                 return result;
>         }
>  
> 
> 
> HTH :)
> 
> --
> Ol
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