Creating feature classes with both Multi and Single geometry types

[CF-FHB-X]

Afternoon!

Quick question regarding creating feature classes with a mixture of both single and multi geometries (i.e. loading a country dataset where some countries are single polygons, whereas others are multi-polygons). What should a user set the shape_type attribute to in that case?

fc = gpkg.create_feature_class(
    'test', srs, fields=fields, shape_type=GeometryType.polygon
)

or

fc = gpkg.create_feature_class(
    'test', srs, fields=fields, shape_type=GeometryType.multi_polygon
)

Additionally, assuming this is something we can do, I assume there's no issue passing a list of mixed-type geometries to the cursor.executemany INSERT statement afterwards?

Thanks!
Richard

[jlhumber]

You could use either approach above but would not recommend trying to mix geometry types, probably depends on your use case which you choose.

• If you used GeometryType.polygon it would be one polygon for each part of a country (e.g. the USA would be a record for Lower 48, a record for Hawaii (each island), a record for Alaska, ... and so on).
• If you used GeometryType.multi_polygon then each record you insert needs to be a MultiPolygon, even is there is just one polygon you'd still make it a MultiPolygon (look at test_multi_polygon for an example of creating a MultiPolygon)

[CF-FHB-X]

I think Option 2 is probably best, otherwise we'd end up with ~300 individual rows for a country like Canada, thanks to all the Arctic islands up north.

I was able to confirm that ArcGIS Pro seems to use the same methodology (all single and multi-polygons are written out as multi-polygons).

There was some discussion on the GeoPackage GitHub page regarding marking those as type GEOMETRY (based on the spec's requirement stating that geometries must be of or a subtype of what's registered in the gpkg_geometry_columns table). Not sure if POLYGON is a subtype of MULTIPOLYGON, or vice versa, but seems GEOMETRY is a bit over-arching.

At any rate, converting everything to MULTIPOLYGON seems easy enough (and supported in Pro)!

Thanks!