[postgis-devel] short question

Paul Ramsey pramsey at cleverelephant.ca
Sat Nov 21 16:16:40 PST 2009


You are constructing empty geometries? Why? (Or is this a question of
curiosity?)

>From an API PoV we should probably make some functions to do this, but
the details are, generally, an LWGEOM with a POINTARRAY that has
npoints = 0. Or, for collections, a collection with ngeoms = 0. I
believe I also consider LWGEOMs with a null POINTARRAY or a null
**geoms to be empty, but I'd have to confirm. The exact way of
representing empty things was never fully documented

P.

On Sat, Nov 21, 2009 at 4:13 PM, Nicklas Avén
<nicklas.aven at jordogskog.no> wrote:
> OK
>
> But what to send as empty when LWLINE or LWPOINT is wanted, not
> LWCOLLECTION.
> internally I mean.
> /Nicklas
>
> 2009-11-22 Paul Ramsey wrote:
>
> No, bad idea. Empty geometries have a type. There's 'POLYGON EMPTY',
>>'LINESTRING EMPTY', etc, etc, etc.
>>
>>P.
>>
>>On Sat, Nov 21, 2009 at 2:04 PM, Nicklas Avén
>> wrote:
>>> is type 0 for LWGEOM occupied by anything or could it be an idea to use
>>> it
>>> for empty geometries.
>>> Then it would be easy to create any emtpy geometry. Like a generic empty
>>> geometry.
>>>
>>> Or is there another way that I have missed.
>>>
>>> When I have identified the empty geometries, in shortestline and it
>>> buddies
>>> I need to communicate that an empty geometry should be returned and the
>>> datatype is LWLINE and LWPOINT for st_closestpoint. I'm tempted to just
>>> make
>>> an LWGEOM with type 0. Is it a bad idea.
>>>
>>> #define EMPTY 0
>>> #define POINTTYPE 1
>>> #define LINETYPE 2
>>> #define POLYGONTYPE 3
>>> and so on
>>>
>>> /Nicklas
>>> _______________________________________________
>>> postgis-devel mailing list
>>> postgis-devel at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>>>
>>>
>>_______________________________________________
>>postgis-devel mailing list
>>postgis-devel at postgis.refractions.net
>>http://postgis.refractions.net/mailman/listinfo/postgis-devel
>>
>>
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>
>



More information about the postgis-devel mailing list