[QGIS-Developer] gpkgext_relations table in gpkg?

[Nyall Dawson]

On Fri, 10 Sept 2021 at 05:58, Richard Duivenvoorde <rdmailings at duif.net> wrote:
>
> Hi Devs,
>
> via:
> https://gis.stackexchange.com/questions/338640/foreign-keys-in-geopackage
> I found:
> http://docs.opengeospatial.org/is/18-000/18-000.html#_gpkgext_relations
> which was new to me...
> BUT for QGIS seems pretty helpfull in finding foreign key relations for domain/lookup tables/widgets?
>
> Anybody experience/examples with this?

It's not supported by GDAL yet -- see
https://gdal.org/drivers/vector/gpkg.html#level-of-support-of-geopackage-extensions
. We'd first need generic API in GDAL for getting/setting
relationships, and then to implement this in the GeoPackage GDAL
driver. Then QGIS would need to use the generic GDAL api to
automatically read and setup the corresponding relationships on
datasets.

It's high on my wishlist too, but we need to make sure it's done
correctly (i.e. upstream in GDAL) and don't hack it in on the QGIS
side alone. There's other formats which store relationship information
(e.g. File/Personal Geodatabases) and we don't want all this
format-specific logic inside QGIS.

(FWIW I've been trying to find a sponsor for this for a while now,
please let me know if you know of any interested parties!)

Nyall