you should look into the history of the gpkg format definition vs spatialite format adoption. Nothing related with QGIS, or gdal or etc etc Luigi Pirelli
************************************************************************************************** * LinkedIn: https://www.linkedin.com/in/luigipirelli * Stackexchange: http://gis.stackexchange.com/users/19667/luigi-pirelli * GitHub: https://github.com/luipir * Mastering QGIS 2nd Edition: * https://www.packtpub.com/big-data-and-business-intelligence/mastering-qgis-second-edition * Hire me: http://goo.gl/BYRQKg ************************************************************************************************** On Thu, 13 Sep 2018 at 14:30, Bo Victor Thomsen <bo.victor.thom...@gmail.com> wrote: > Ok.. From the Spatialite 4.2.0 wiki: > > > - *CastAutomagic()*: will indifferently accept both GPKG and > SpatiaLite BLOB Geometries, then returning anyway a SpatiaLite's own BLOB > Geometry. > > > I can confirm, that using the "CastAutomagic(geom)" function instead of > the simple field "geom" will get the st_area and other ogc functions in > the QGIS Databasemanager Dataprovider for GeoPackage to work. > > That means that the geopackage binary format for geometry is incompatible > with the underlying spatialite spatial system and functions. > > This is *not* the most helpful and thoughtful user oriented solution I've > encountered ... Or should I have RTFM somewhere in the QGIS.org site ? > > However it does work. Thanks for the tip > > > > > Den tor. 13. sep. 2018 kl. 13.20 skrev Jean-Baptiste Desbas < > jb.des...@gmail.com>: > >> Hi, >> >> I have to use *st_area(CastAutomagic(geom)) *instead of *st_area(geom)*, >> otherwise null column is retourned. >> >> Le jeu. 13 sept. 2018 à 11:45, Bo Victor Thomsen < >> bo.victor.thom...@gmail.com> a écrit : >> >>> Hi Lene - >>> >>> I've made a few observations regarding the use of GeoPackage in >>> DBManager... >>> >>> I have a *GeoPackage* based table called "renhold" containing polygons. >>> Primary key column is an integer called "fid" and the geometry column is >>> called "geom" - It's pretty close to your setup >>> >>> If I use the *DBManager* with the *GeoPackage *dataprovider and execute >>> the following statement: *select fid, st_area (geom) from renhold , *it >>> returns a table with 2 columns as expected. However , column nr. 2 contains >>> only nulls. However, the statement does not result in an error. The >>> function "st_area" simply doesn't return a value besides null. >>> >>> An now the mystery!! : >>> >>> If I use the *DBManager* with the *Virtual Layers -> Project layers >>> *dataprovider >>> and execute the following statement: *select fid, st_area (geometry) >>> from renhold , *it returns a table with 2 columns as expected. And >>> column nr. 2 do contain the expected area values. Go figure... >>> >>> NB! The "renhold" layer is visible in the map and named "renhold" >>> NBB! In the *Virtual Layers* dataprovider you have to use the standard >>> name "geometry" to represent the geometry column - not the real column name >>> ("geom" in this case) >>> >>> Actually I have a reasonable explanation: The 2 different dataproviders >>> uses different internal functions to calculate the area. However the >>> function used by the GeoPackage Dataprovider doesn't work ! >>> >>> >>> Regards >>> Bo Victor Thomsen >>> LIFA Denamrk >>> >>> Den tor. 13. sep. 2018 kl. 09.27 skrev Alexandre Neto < >>> senhor.n...@gmail.com>: >>> >>>> Hi Lee, >>>> >>>> Can you try removing the quotation marks around geom? >>>> >>>> Best wishes, >>>> >>>> Alex Neto >>>> >>>> A qui, 13/09/2018, 02:04, Lene Fischer <l...@ign.ku.dk> escreveu: >>>> >>>>> Hi, >>>>> Trying out a geopackage layer in DBManager asking a simple SQL >>>>> statement st_area >>>>> But when I try to write a statement like this >>>>> >>>>> SELECT "vandopland".* , st_area("vandopland"."geom") as areal_m2 >>>>> FROM "vandopland" >>>>> >>>>> "geom" is not found. Suggestions as geomfromexifgpsblob or >>>>> geomfromfgf or geomfromwkb . Then I get "an error occured" >>>>> >>>>> Any suggestions what I might have done wrong. >>>>> >>>>> Regards from a newbee Geopagkace/DBmanager >>>>> >>>>> Lene Fischer >>>>> >>>>> >>>>> _______________________________________________ >>>>> Qgis-user mailing list >>>>> Qgis-user@lists.osgeo.org >>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> >>>> -- >>>> Alexandre Neto >>>> --------------------- >>>> @AlexNetoGeo >>>> http://sigsemgrilhetas.wordpress.com >>>> http://gisunchained.wordpress.com >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> Qgis-user@lists.osgeo.org >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> >>> >>> >>> -- >>> Med venlig hilsen >>> >>> Bo Victor Thomsen >>> >>> _______________________________________________ >>> Qgis-user mailing list >>> Qgis-user@lists.osgeo.org >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> >> > > -- > Med venlig hilsen > > Bo Victor Thomsen > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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