fix: make GeometryBounds serializable for zone-map persistence

The zoned writer serializes each zone stat descriptor to persist it, but GeometryBounds used the default (non-serializable), so writing a geometry column zone map failed at write time. Add serialize/deserialize (no options) plus a regression test.

Signed-off-by: Nemo Yu <zyu379@wisc.edu>

Author: HarukiMoriarty

vortex-geo/src/aggregate_fn/bounds.rs

@@ -23,6 +23,7 @@ use vortex_array::dtype::StructFields;
 use vortex_array::scalar::Scalar;
 use vortex_error::VortexResult;
 use vortex_error::vortex_err;
+use vortex_session::VortexSession;
 
 use crate::extension::coordinates;
 use crate::extension::is_native_geometry;
@@ -112,6 +113,15 @@ impl AggregateFnVTable for GeometryBounds {
         AggregateFnId::new("vortex.geo.bounds")
     }
 
+    // Serializable so the zoned writer can persist this as a per-chunk stat. No options to encode.
+    fn serialize(&self, _options: &Self::Options) -> VortexResult<Option<Vec<u8>>> {
+        Ok(Some(vec![]))
+    }
+
+    fn deserialize(&self, _metadata: &[u8], _session: &VortexSession) -> VortexResult<Self::Options> {
+        Ok(EmptyOptions)
+    }
+
     fn return_dtype(&self, _options: &Self::Options, input_dtype: &DType) -> Option<DType> {
         is_native_geometry(input_dtype).then(bounds_dtype)
     }
@@ -217,6 +227,7 @@ impl AggregateFnVTable for GeometryBounds {
 mod tests {
     use vortex_array::VortexSessionExecute;
     use vortex_array::aggregate_fn::Accumulator;
+    use vortex_array::aggregate_fn::AggregateFnVTable;
     use vortex_array::aggregate_fn::DynAccumulator;
     use vortex_array::aggregate_fn::EmptyOptions;
     use vortex_array::scalar::Scalar;
@@ -227,6 +238,17 @@ mod tests {
     use crate::test_harness::point_column;
     use crate::test_harness::polygon_column;
 
+    /// The aggregate must be serializable so the zoned writer can persist its zone-stat descriptor.
+    #[test]
+    fn serializes_for_zone_storage() -> VortexResult<()> {
+        let session = vortex_array::array_session();
+        let metadata = GeometryBounds
+            .serialize(&EmptyOptions)?
+            .expect("GeometryBounds must be serializable to be stored as a zone statistic");
+        GeometryBounds.deserialize(&metadata, &session)?;
+        Ok(())
+    }
+
     /// The MBR result's corners as `(xmin, ymin, xmax, ymax)`.
     fn mbr(result: &Scalar) -> VortexResult<(f64, f64, f64, f64)> {
         let fields = result.as_struct();