Empty geometries and Mutable arrays

[JosiahParry]

The MutablePointArray provides a method push_empty() which allows us to push an empty geometry. This is helpful where I have Option<PointTrait> with None. However, other mutable geometry arrays do not have the push_empty() method. I do note, that they require an Option<&impl GeometryTrait>. Is the empty geometry appropriately created in the None case?

[kylebarron]

I think the (warranted) confusion here is between "invalid/null/missing", "valid but empty", and "valid and non-empty" geometries. Most geospatial tools don't have a separate validity buffer, but Arrow does, which allows us to have a rich understanding of the data.

I think of the three as:

• Null: You have a row of data that doesn't have any geometry associated with it
• Valid but empty: the result of an intersection between two polygons where the polygons don't intersect at all. Aka POINT EMPTY in WKT. The operation didn't fail... the geometry isn't missing... it returned with an empty result.
• Valid but nonempty: an intersection with non-empty output.

[kylebarron]

The GeoPandas guide on this is relevant too: https://geopandas.org/en/stable/docs/user_guide/missing_empty.html