[postgis-devel] isvalid(geom), but st_ashexewkb(geom, 'NDR')::geometry fails

[Obe, Regina]

David,

I don't think that is valid WKT syntax for an EMPTY multipolygon. If I try to stuff that in via ST_GeomFromText it returns invalid geometry. Not sure how you got that in there.

It should be

 SELECT ST_GeomFromText('MULTIPOLYGON EMPTY');


On 1.3.3 and 1.3.4SVN - when I do this - I get the below which is also kind of odd.  I would have expected it to maintain the empty polygon.

 SELECT ST_IsValid(the_geom), ST_AsText(the_geom), ST_IsEmpty(the_geom), ST_AsEWKT(the_geom)  FROM (SELECT ST_GeomFromText('MULTIPOLYGON EMPTY') As the_geom) As foo ;
 st_isvalid |        st_astext         | st_isempty |        st_asewkt         
------------+--------------------------+------------+--------------------------
 t          | GEOMETRYCOLLECTION EMPTY | t          | GEOMETRYCOLLECTION EMPTY
(1 row)

Hope that helps,
Regina
-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net on behalf of David Fuhry
Sent: Thu 10/23/2008 11:28 PM
To: PostGIS Development Discussion
Subject: [postgis-devel] isvalid(geom), but st_ashexewkb(geom,'NDR')::geometry fails
 
I have an empty multipolygon which isvalid(), but which the parser 
throws "ERROR:  geometry requires more points" on.  Is this a bug in 
isvalid(), or in the parser?  Interestingly, st_isempty() returns false.

db=> select geom from tt;
                          geom
------------------------------------------------------
  0106000020C90E00000100000001030000000100000000000000
(1 row)

db=> select st_astext(geom) from tt;
        st_astext
------------------------
  MULTIPOLYGON(( EMPTY))
(1 row)

db=> select isvalid(geom) from tt;
  isvalid
---------
  t
(1 row)

db=> select st_ashexewkb(geom,'NDR')::geometry from tt;
ERROR:  geometry requires more points

db=> select st_isempty(geom) from tt;
  st_isempty
------------
  f
(1 row)

db=> select version(), postgis_version();
                                         version 
                  |            postgis_version
-----------------------------------------------------------------------
-----------------+---------------------------------------
  PostgreSQL 8.3.1 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.2.3 
(Debian 4.2.3-4) | 1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
(1 row)

Thanks,

Dave
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