feat(vortex-geo): add MultiPolygon extension type + WKB export for native geometry

Cargo.toml

@@ -165,6 +165,7 @@ geo = "0.31.0"
 geo-traits = "0.3.0"
 geo-types = "0.7.19"
 geoarrow = "0.8.0"
+geoarrow-cast = "0.8.0"
 get_dir = "0.5.0"
 glob = "0.3.2"
 goldenfile = "1"

vortex-geo/Cargo.toml

@@ -20,6 +20,7 @@ geo = { workspace = true }
 geo-traits = { workspace = true }
 geo-types = { workspace = true }
 geoarrow = { workspace = true }
+geoarrow-cast = { workspace = true }
 prost = { workspace = true }
 vortex-array = { workspace = true }
 vortex-error = { workspace = true }

vortex-geo/src/extension/mod.rs

@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 pub(crate) mod coordinate;
+mod multipolygon;
 mod point;
 mod polygon;
 mod wkb;
@@ -10,8 +11,13 @@ use std::fmt::Display;
 use std::sync::Arc;
 
 use geo_types::Geometry;
+use geoarrow::array::GeoArrowArray;
 use geoarrow::datatypes::Crs;
+use geoarrow::datatypes::GeoArrowType;
 use geoarrow::datatypes::Metadata;
+use geoarrow::datatypes::WkbType;
+use geoarrow_cast::cast::cast;
+pub use multipolygon::*;
 pub use point::*;
 pub use polygon::*;
 use vortex_array::ArrayRef;
@@ -20,6 +26,7 @@ use vortex_array::IntoArray;
 use vortex_array::arrays::ConstantArray;
 use vortex_array::arrays::ExtensionArray;
 use vortex_array::arrays::extension::ExtensionArrayExt;
+use vortex_array::arrow::FromArrowArray;
 use vortex_array::scalar::Scalar;
 use vortex_error::VortexResult;
 use vortex_error::vortex_bail;
@@ -46,6 +53,8 @@ pub(crate) fn geometries(
         point_geometries(&storage, ctx)
     } else if ext.is::<Polygon>() {
         polygon_geometries(&storage, ctx)
+    } else if ext.is::<MultiPolygon>() {
+        multipolygon_geometries(&storage, ctx)
     } else {
         vortex_bail!("geo: unsupported geometry extension {}", array.dtype())
     }
@@ -95,6 +104,15 @@ pub(crate) fn geoarrow_metadata(geo_metadata: &GeoMetadata) -> Arc<Metadata> {
     ))
 }
 
+/// Serialize a native geometry array to WKB (a `WkbView` array) via geoarrow's cast.
+/// Shared by the `to_wkb` methods on the geometry extension types.
+pub(crate) fn geoarrow_to_wkb(geo_array: &dyn GeoArrowArray) -> VortexResult<ArrayRef> {
+    let wkb_type = GeoArrowType::WkbView(WkbType::new(geoarrow_metadata(&GeoMetadata::default())));
+    let wkb = cast(geo_array, &wkb_type)
+        .map_err(|e| vortex_err!("failed to cast geometry to WKB: {e}"))?;
+    ArrayRef::from_arrow(wkb.to_array_ref().as_ref(), false)
+}
+
 /// Recover [`GeoMetadata`] from GeoArrow metadata.
 pub(crate) fn geo_metadata_from_arrow(metadata: &Metadata) -> GeoMetadata {
     let crs = metadata.crs().crs_value().map(|value| {