[Qgis-user] Is QGIS showing the records with geometry NULL

[Rahkonen Jukka (MML)]

Hi,

We spent some time with empty geometries in OpenJUMP and I attach some test data from those experiments. Feel free to use it in the QGIS feature request. Zip contains point, line, and polygon shapefiles, each having 8 features but only one feature with geometry.  From the WKT files you can see that there are actually different kind of empty geometries. I even did not bother to think about Z, M, and ZM geometries.

POINT EMPTY
MULTIPOINT EMPTY
LINESTRING EMPTY
MULTILINESTRING EMPTY
POLYGON EMPTY
MULTIPOLYGON EMPTY
GEOMETRYCOLLECTION EMPTY

One may say that empty is always just empty but one needs also to think what happens if user copies POLYGON EMPTY and tries to paste it into a point layer. Should copy be denied or empty geometry converted into POINT EMPTY? For OpenJUMP that does not matter because it can handle all kind of geometries on the same layer. However, saving POINT EMPTY into polygon shapefile may fail and therefore OpenJUMP can convert even empty geometries like POINT EMPTY ->POLYGON EMPTY.

-Jukka Rahkonen-

Andrea Peri wrote:

Hi Jukka,
yes is exactly this the question.

The QGIS don't show any record with null geometry so is impossible for me to add a geometry to it. Or delete it definitivelly.

But the record with null geometry is however saved when I export the shapefile from qgis.

So the QGIS show me 14 records but export a shapefile with 16 records
(2 records has null geometry).

So when load it in a spatialite or on a postgis environment or open it using another GIS like arcview3 from esri.
I see this two more records with null geometry.

AFAIK this is a chaotic situation for who work using qgis and produce a shapefile to distribute to other users that has other gis softwares.

A.


2016-05-26 10:24 GMT+02:00 Jukka Rahkonen <jukka.rahkonen at maanmittauslaitos.fi>:
> Nicolas Cadieux <nicolas.cadieux at ...> writes:
>
>>
>>
>> Hi,
>> Is it possible that the 2 missing records were deleted in another GIS?
> There is an issue with deleting records in shape file as there are 
> many ways to do that.  If the record were deleted in another GIS, they 
> may show up (or
> not) in another software. Could that be it...
>> Nicolas
>
> Hi,
>
> I suppose that Andrea means a valid situation with real existing 
> features which just do not have geometry. They are valid in shapefiles 
> but many GIS software have difficulties in dealing with them. 
> Naturally they cannot be showed on the map and spatial queries can't 
> find them but they should be found from attribute view and be editable there.
>
> -Jukka Rahkonen-
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--
-----------------
Andrea Peri
. . . . . . . . .
qwerty àèìòù
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