[postgis-devel] POINT EMPTY in WKB

[Paragon Corporation]

 Though they seem to maintain the input display regardless.

What I the difference between these two geometries?

  SELECT Geometry::STGeomFromText('MULTIPOINT(EMPTY)',0).STAsText();

Yields:  MULTIPOINT (EMPTY)

   SELECT Geometry::STGeomFromText('MULTIPOINT EMPTY',0).STAsText();

Yields: MULTIPOINT EMPTY

Do we make a distinction between those?  




-----Original Message-----
From: Paragon Corporation [mailto:lr at pcorp.us] 
Sent: Monday, December 06, 2010 4:09 PM
To: 'PostGIS Development Discussion'
Subject: RE: [postgis-devel] POINT EMPTY in WKB

On my SQL Server 2008 the below 

 SELECT Geometry::STGeomFromText('POINT EMPTY',0).STAsText(); 


Yields:
POINT EMPTY

Though I don't have the SQL server 2011 installed so who knows what that
returns.  It sounds like in next release they've got a pretty beefed up
curved support.  Even geodetic curved support and got rid of their
hemisphere restriction.

And 

  SELECT Geometry::STGeomFromText('POINT(EMPTY)',0).STAsText();

Throws an error

A .NET Framework error occurred during execution of user-defined routine or
aggregate "geometry": 
System.FormatException: 24141: A number is expected at position 11 of the
input. The input has EMPTY.
System.FormatException: 
   at Microsoft.SqlServer.Types.OpenGisWktReader.RecognizeDouble()
   at Microsoft.SqlServer.Types.OpenGisWktReader.ParsePointText(Boolean
parseParentheses)
   at Microsoft.SqlServer.Types.OpenGisWktReader.ParseTaggedText(OpenGisType
type)
   at Microsoft.SqlServer.Types.OpenGisWktReader.Read(OpenGisType type,
Int32 srid)
   at Microsoft.SqlServer.Types.SqlGeometry.GeometryFromText(OpenGisType
type, SqlChars text, Int32 srid) .

But I'm not running R2 version I don't think:

Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (X64)   Jul  9 2008 14:17:44
Copyright (c) 1988-2008 Microsoft Corporation  Standard Edition (64-bit) on
Windows NT 5.2 <X64> (Build 3790: Service Pack 2) 


-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net
[mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Paul
Ramsey
Sent: Monday, December 06, 2010 4:00 PM
To: PostGIS Development Discussion
Subject: Re: [postgis-devel] POINT EMPTY in WKB

It's just POINT EMPTY. Everything else has a representation. In fact, I
think Mats checked for me and SQLServer uses the same semantic as I am for
empties in WKB, npoints=0 or ngeoms=0 or nrings=0 depending on the type
being represented.

And I think for POINT EMPTY they transform to GEOMETRYCOLLECTION EMPTY.
(which is what we do now, see

  SELECT AsText('POINT EMPTY'::geometry);

P.

On Mon, Dec 6, 2010 at 12:48 PM, Paragon Corporation <lr at pcorp.us> wrote:
>
>
>> A final possibility would be to hack POINT EMPTY into WKB, as 
>> something like POINT(nan nan nan) or POINT(inf inf inf) or POINT(-0 
>> -0 -0). There would be a danger there in platforms that have 
>> different interpretations of what nan, inf or -0 are in binary.
>
> I the only issue with POINT EMPTY or ..anyspecifictype EMPTY
>
> I'm a bit bothered about the dump issue you describe -- not being able 
> to restore exactly what you thought you had.
>
> Thanks,
> Regina
>
>
>
> _______________________________________________
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> postgis-devel at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>
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