paleolimbot commented on code in PR #476:
URL: https://github.com/apache/sedona-db/pull/476#discussion_r2658694796


##########
python/sedonadb/tests/functions/test_functions.py:
##########
@@ -827,17 +827,70 @@ def test_st_convexhull(eng, geom, expected):
             "GEOMETRYCOLLECTION (POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0)), POLYGON 
((1 0, 2 0, 2 1, 1 1, 1 0)))",
             "POLYGON ((0 0, 0 1, 1 1, 2 1, 2 0, 1 0, 0 0))",
         ),
+        # Z and M support
+        ("POINT Z (0 0 0)", "POINT Z(0 0 0)"),
+        ("POINT M (1 2 3)", "POINT M(1 2 3)"),
+        ("POINT ZM (1 2 3 4)", "POINT ZM(1 2 3 4)"),
+        ("LINESTRING Z (0 0 0, 1 1 1)", "LINESTRING Z(0 0 0,1 1 1)"),
+        ("LINESTRING M (0 0 1, 1 1 2)", "LINESTRING M(0 0 1,1 1 2)"),
+        ("LINESTRING ZM (0 0 1 2, 1 1 3 4)", "LINESTRING ZM(0 0 1 2,1 1 3 4)"),
+        (
+            "POLYGON Z ((0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10))",
+            "POLYGON Z((0 0 10,4 0 10,4 4 10,0 4 10,0 0 10))",
+        ),
+        (
+            "POLYGON M ((0 0 1, 4 0 2, 4 4 3, 0 4 4, 0 0 5))",
+            "POLYGON M((0 0 1,4 0 2,4 4 3,0 4 4,0 0 5))",
+        ),
+        (
+            "POLYGON ZM ((0 0 10 1, 4 0 10 2, 4 4 10 3, 0 4 10 4, 0 0 10 5))",
+            "POLYGON ZM((0 0 10 1,4 0 10 2,4 4 10 3,0 4 10 4,0 0 10 5))",
+        ),
+        ("MULTIPOINT Z ((0 0 0), (1 1 1))", "MULTIPOINT Z((0 0 0),(1 1 1))"),
+        ("MULTIPOINT M ((0 0 1), (1 1 2))", "MULTIPOINT M((0 0 1),(1 1 2))"),
+        ("MULTIPOINT ZM ((0 0 1 2), (1 1 3 4))", "MULTIPOINT ZM((0 0 1 2),(1 1 
3 4))"),
+        # Polygons overlap, so it's reduced to a single one
+        (
+            "MULTIPOLYGON Z (((0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10)), ((1 1 
5, 1 2 5, 2 2 5, 2 1 5, 1 1 5)))",
+            "POLYGON Z((0 4 10,4 4 10,4 0 10,0 0 10,0 4 10))",
+        ),
+        # Skipping M and ZM tests because library is not smart enough for M 
dimensions yet. (specifies NaN instead)
+        (
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3), LINESTRING Z(0 0 0,1 1 1))",
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3),LINESTRING Z(0 0 0,1 1 1))",
+        ),
+        # dimension specified on nested geometries, but not outer 
geometrycollection
+        (
+            "GEOMETRYCOLLECTION (POINT Z(1 2 3), LINESTRING Z(0 0 0,1 1 1))",
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3),LINESTRING Z(0 0 0,1 1 1))",
+        ),
+        # Skipping M and ZM tests because library is not smart enough for 
GeometryCollection M yet , specifies NaN instead)
     ],
 )
 def test_st_unaryunion(eng, geom, expected):
+    is_postgis = eng == PostGIS
     eng = eng.create_or_skip()
 
     if expected is None:
         eng.assert_query_result(f"SELECT ST_UnaryUnion({geom_or_null(geom)})", 
expected)
+    # PostGIS doesn't support M dimensions so we skip the test
+    elif is_postgis and (" M" in expected or "ZM" in expected):

Review Comment:
   Instead of the `if` statements here, can this be a separate test?



##########
c/sedona-geos/src/geos_to_wkb.rs:
##########
@@ -0,0 +1,503 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+use std::io::Write;
+
+use byteorder::{LittleEndian, WriteBytesExt};
+use datafusion_common::{error::Result, exec_err, DataFusionError};
+use geos::{Geom, Geometry, GeometryTypes};
+
+// TODO:
+const NATIVE_ENDIANNESS: u8 = 1;
+
+/// Write a GEOS geometry to WKB format.
+///
+/// This is a fast, custom implementation that directly extracts coordinates
+/// from GEOS geometries and writes them in WKB format into a buffer.
+pub fn write_geos_geometry(geom: &Geometry, writer: &mut impl Write) -> 
Result<()> {

Review Comment:
   (Native or little endian, whichever is easier) ISO WKB is the only thing we 
need to support here...our SRID support is handled outside of GEOS/Wkb (as a 
struct with the crs in a separate column).



##########
python/sedonadb/tests/functions/test_functions.py:
##########
@@ -827,17 +827,70 @@ def test_st_convexhull(eng, geom, expected):
             "GEOMETRYCOLLECTION (POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0)), POLYGON 
((1 0, 2 0, 2 1, 1 1, 1 0)))",
             "POLYGON ((0 0, 0 1, 1 1, 2 1, 2 0, 1 0, 0 0))",
         ),
+        # Z and M support
+        ("POINT Z (0 0 0)", "POINT Z(0 0 0)"),
+        ("POINT M (1 2 3)", "POINT M(1 2 3)"),
+        ("POINT ZM (1 2 3 4)", "POINT ZM(1 2 3 4)"),
+        ("LINESTRING Z (0 0 0, 1 1 1)", "LINESTRING Z(0 0 0,1 1 1)"),
+        ("LINESTRING M (0 0 1, 1 1 2)", "LINESTRING M(0 0 1,1 1 2)"),
+        ("LINESTRING ZM (0 0 1 2, 1 1 3 4)", "LINESTRING ZM(0 0 1 2,1 1 3 4)"),
+        (
+            "POLYGON Z ((0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10))",
+            "POLYGON Z((0 0 10,4 0 10,4 4 10,0 4 10,0 0 10))",
+        ),
+        (
+            "POLYGON M ((0 0 1, 4 0 2, 4 4 3, 0 4 4, 0 0 5))",
+            "POLYGON M((0 0 1,4 0 2,4 4 3,0 4 4,0 0 5))",
+        ),
+        (
+            "POLYGON ZM ((0 0 10 1, 4 0 10 2, 4 4 10 3, 0 4 10 4, 0 0 10 5))",
+            "POLYGON ZM((0 0 10 1,4 0 10 2,4 4 10 3,0 4 10 4,0 0 10 5))",
+        ),
+        ("MULTIPOINT Z ((0 0 0), (1 1 1))", "MULTIPOINT Z((0 0 0),(1 1 1))"),
+        ("MULTIPOINT M ((0 0 1), (1 1 2))", "MULTIPOINT M((0 0 1),(1 1 2))"),
+        ("MULTIPOINT ZM ((0 0 1 2), (1 1 3 4))", "MULTIPOINT ZM((0 0 1 2),(1 1 
3 4))"),
+        # Polygons overlap, so it's reduced to a single one
+        (
+            "MULTIPOLYGON Z (((0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10)), ((1 1 
5, 1 2 5, 2 2 5, 2 1 5, 1 1 5)))",
+            "POLYGON Z((0 4 10,4 4 10,4 0 10,0 0 10,0 4 10))",
+        ),
+        # Skipping M and ZM tests because library is not smart enough for M 
dimensions yet. (specifies NaN instead)
+        (
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3), LINESTRING Z(0 0 0,1 1 1))",
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3),LINESTRING Z(0 0 0,1 1 1))",
+        ),
+        # dimension specified on nested geometries, but not outer 
geometrycollection
+        (
+            "GEOMETRYCOLLECTION (POINT Z(1 2 3), LINESTRING Z(0 0 0,1 1 1))",
+            "GEOMETRYCOLLECTION Z(POINT Z(1 2 3),LINESTRING Z(0 0 0,1 1 1))",
+        ),
+        # Skipping M and ZM tests because library is not smart enough for 
GeometryCollection M yet , specifies NaN instead)
     ],
 )
 def test_st_unaryunion(eng, geom, expected):
+    is_postgis = eng == PostGIS
     eng = eng.create_or_skip()
 
     if expected is None:
         eng.assert_query_result(f"SELECT ST_UnaryUnion({geom_or_null(geom)})", 
expected)
+    # PostGIS doesn't support M dimensions so we skip the test
+    elif is_postgis and (" M" in expected or "ZM" in expected):
+        pytest.skip("PostGIS doesn't support M dimensions")
+    # TODO: temp solution for now. how to test postgis for equality and 
ST_Equals() only tests for 2D (yes, it does pass)
+    elif is_postgis and "Z" in expected:  # and "MULTIPOLYGON" not in expected:
+        pytest.skip(
+            "Temporarily skip PostGIS z tests for now since WKT is spaced 
differently, and ST_Equals() doesn't work"
+        )
     elif "EMPTY" in expected.upper():
         eng.assert_query_result(
             f"SELECT ST_IsEmpty(ST_UnaryUnion({geom_or_null(geom)}))", True
         )
+    # ST_Equals() (in the else case) doesn't test for Z and M dimensions so we 
test for string equality for 3-4D
+    elif "Z" in expected.upper() or "M " in expected.upper():

Review Comment:
   I hope string equality works here...the alternative would probably be to 
check for 2D equality and then dump the coordinates and check for equal z/m 
values (maybe by sorting them and checking Python list equality?)



##########
c/sedona-geos/src/geos_to_wkb.rs:
##########
@@ -0,0 +1,503 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+use std::io::Write;
+
+use byteorder::{LittleEndian, WriteBytesExt};
+use datafusion_common::{error::Result, exec_err, DataFusionError};
+use geos::{Geom, Geometry, GeometryTypes};
+
+// TODO:
+const NATIVE_ENDIANNESS: u8 = 1;
+
+/// Write a GEOS geometry to WKB format.
+///
+/// This is a fast, custom implementation that directly extracts coordinates
+/// from GEOS geometries and writes them in WKB format into a buffer.
+pub fn write_geos_geometry(geom: &Geometry, writer: &mut impl Write) -> 
Result<()> {
+    write_geometry(geom, writer)
+}
+
+fn write_geometry(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    let geom_type = geom
+        .geometry_type()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get 
geometry type: {e}")))?;
+
+    match geom_type {
+        GeometryTypes::Point => write_point(geom, writer),
+        GeometryTypes::LineString => write_line_string(geom, writer),
+        GeometryTypes::Polygon => write_polygon(geom, writer),
+        GeometryTypes::MultiPoint => write_multi_point(geom, writer),
+        GeometryTypes::MultiLineString => write_multi_line_string(geom, 
writer),
+        GeometryTypes::MultiPolygon => write_multi_polygon(geom, writer),
+        GeometryTypes::GeometryCollection => write_geometry_collection(geom, 
writer),
+        _ => Err(DataFusionError::Execution(format!(
+            "Unsupported geometry type: {geom_type:?}"
+        ))),
+    }
+}
+
+fn write_point(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    // Write byte order
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 1,   // Point
+        (true, false) => 1001, // Point Z
+        (false, true) => 2001, // Point M
+        (true, true) => 3001,  // Point ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        // Write NaN coordinates for empty point
+        writer.write_f64::<LittleEndian>(f64::NAN)?; // x
+        writer.write_f64::<LittleEndian>(f64::NAN)?; // y
+        if has_z {
+            writer.write_f64::<LittleEndian>(f64::NAN)?; // z
+        }
+        if has_m {
+            writer.write_f64::<LittleEndian>(f64::NAN)?; // m
+        }
+    } else {
+        let coord_seq = geom
+            .get_coord_seq()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
coord seq: {e}")))?;
+
+        let num_coords = coord_seq.size().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get coord seq size: 
{e}"))
+        })?;
+
+        if num_coords == 0 {
+            return exec_err!("Point has no coordinates");
+        }
+
+        write_coord_seq(&coord_seq, writer, has_z, has_m)?;
+    }
+
+    Ok(())
+}
+
+fn write_line_string(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 2,   // LineString
+        (true, false) => 1002, // LineString Z
+        (false, true) => 2002, // LineString M
+        (true, true) => 3002,  // LineString ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 points
+    } else {
+        let coord_seq = geom
+            .get_coord_seq()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
coord seq: {e}")))?;
+
+        let num_points = coord_seq.size().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get coord seq size: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_points as u32)?;
+
+        write_coord_seq(&coord_seq, writer, has_z, has_m)?;
+    }
+
+    Ok(())
+}
+
+fn write_polygon(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 3,   // Polygon
+        (true, false) => 1003, // Polygon Z
+        (false, true) => 2003, // Polygon M
+        (true, true) => 3003,  // Polygon ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 rings
+    } else {
+        let exterior = geom
+            .get_exterior_ring()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
exterior ring: {e}")))?;
+
+        let exterior_coord_seq = exterior.get_coord_seq().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get exterior coord 
seq: {e}"))
+        })?;
+
+        let num_interior_rings = geom.get_num_interior_rings().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num interior 
rings: {e}"))
+        })?;
+
+        // Number of rings (interior rings + 1 exterior ring)
+        writer.write_u32::<LittleEndian>((num_interior_rings + 1) as u32)?;
+
+        let exterior_size = exterior_coord_seq
+            .size()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
exterior size: {e}")))?;
+
+        // Number of points in exterior ring
+        writer.write_u32::<LittleEndian>(exterior_size as u32)?;
+        write_coord_seq(&exterior_coord_seq, writer, has_z, has_m)?;
+
+        // Write interior rings
+        for i in 0..num_interior_rings {
+            let interior = geom.get_interior_ring_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
ring {i}: {e}"))
+            })?;
+
+            let interior_coord_seq = interior.get_coord_seq().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
coord seq: {e}"))
+            })?;
+
+            let interior_size = interior_coord_seq.size().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
size: {e}"))
+            })?;
+
+            writer.write_u32::<LittleEndian>(interior_size as u32)?;
+            write_coord_seq(&interior_coord_seq, writer, has_z, has_m)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_point(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 4,   // MultiPoint
+        (true, false) => 1004, // MultiPoint Z
+        (false, true) => 2004, // MultiPoint M
+        (true, true) => 3004,  // MultiPoint ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 points
+    } else {
+        let num_points = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_points as u32)?;
+
+        for i in 0..num_points {
+            let point = geom
+                .get_geometry_n(i)
+                .map_err(|e| DataFusionError::Execution(format!("Failed to get 
point {i}: {e}")))?;
+
+            write_point(&point, writer)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_line_string(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 5,   // MultiLineString
+        (true, false) => 1005, // MultiLineString Z
+        (false, true) => 2005, // MultiLineString M
+        (true, true) => 3005,  // MultiLineString ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 line strings
+    } else {
+        let num_line_strings = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_line_strings as u32)?;
+
+        for i in 0..num_line_strings {
+            let ls = geom.get_geometry_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get line string 
{i}: {e}"))
+            })?;
+
+            write_line_string(&ls, writer)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_polygon(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 6,   // MultiPolygon
+        (true, false) => 1006, // MultiPolygon Z
+        (false, true) => 2006, // MultiPolygon M
+        (true, true) => 3006,  // MultiPolygon ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 polygons
+    } else {
+        let num_polygons = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_polygons as u32)?;
+
+        for i in 0..num_polygons {
+            let poly = geom.get_geometry_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get polygon {i}: 
{e}"))
+            })?;
+
+            write_polygon(&poly, writer)?;
+        }
+    }
+    Ok(())
+}
+
+fn write_geometry_collection(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    // GeometryCollection's dimension might be specified on the child 
geometries only
+    let dimension = get_geomcol_dimension(geom)?;
+    writer.write_u32::<LittleEndian>(dimension)?;
+
+    let num_geometries = geom
+        .get_num_geometries()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get num 
geometries: {e}")))?;
+
+    writer.write_u32::<LittleEndian>(num_geometries as u32)?;
+
+    for i in 0..num_geometries {
+        let sub_geom = geom
+            .get_geometry_n(i)
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
geometry {i}: {e}")))?;
+
+        write_geometry(&sub_geom, writer)?;
+    }
+
+    Ok(())
+}
+
+// TBH. um not sure this is needed for geos
+fn get_geomcol_dimension(geomcol: &impl Geom) -> Result<u32> {

Review Comment:
   I suppose removing this and seeing if your tests still pass would do it? If 
not this workaround seems fine to me (it's theoretically slower, but only 
slower for geometry collections and that's not something at least I'm super 
worried about the performance implications of)



##########
python/sedonadb/tests/functions/test_functions.py:
##########
@@ -874,17 +827,70 @@ def test_st_convexhull(eng, geom, expected):
             "GEOMETRYCOLLECTION (POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0)), POLYGON 
((1 0, 2 0, 2 1, 1 1, 1 0)))",
             "POLYGON ((0 0, 0 1, 1 1, 2 1, 2 0, 1 0, 0 0))",
         ),
+        # Z and M support
+        ("POINT Z (0 0 0)", "POINT Z(0 0 0)"),
+        ("POINT M (1 2 3)", "POINT M(1 2 3)"),
+        ("POINT ZM (1 2 3 4)", "POINT ZM(1 2 3 4)"),
+        ("LINESTRING Z (0 0 0, 1 1 1)", "LINESTRING Z(0 0 0,1 1 1)"),

Review Comment:
   That's a good catch! We should definitely keep these tests.



##########
Cargo.toml:
##########
@@ -100,12 +101,11 @@ mimalloc = { version = "0.1", default-features = false }
 libmimalloc-sys = { version = "0.1", default-features = false }
 once_cell = "1.20"
 
-geos = { git="https://github.com/georust/geos.git";, 
rev="47afbad2483e489911ddb456417808340e9342c3", features = ["geo", "v3_11_0"] }
+geos = { git="https://github.com/georust/geos.git";, 
rev="47afbad2483e489911ddb456417808340e9342c3", features = ["geo", "v3_12_0"] }

Review Comment:
   GEOS 3.12 is in Ubuntu 24.04 and so I don't think will be a problem for CI 
or contributors!



##########
c/sedona-geos/src/geos_to_wkb.rs:
##########
@@ -0,0 +1,503 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+use std::io::Write;
+
+use byteorder::{LittleEndian, WriteBytesExt};
+use datafusion_common::{error::Result, exec_err, DataFusionError};
+use geos::{Geom, Geometry, GeometryTypes};
+
+// TODO:
+const NATIVE_ENDIANNESS: u8 = 1;
+
+/// Write a GEOS geometry to WKB format.
+///
+/// This is a fast, custom implementation that directly extracts coordinates
+/// from GEOS geometries and writes them in WKB format into a buffer.
+pub fn write_geos_geometry(geom: &Geometry, writer: &mut impl Write) -> 
Result<()> {
+    write_geometry(geom, writer)
+}
+
+fn write_geometry(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    let geom_type = geom
+        .geometry_type()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get 
geometry type: {e}")))?;
+
+    match geom_type {
+        GeometryTypes::Point => write_point(geom, writer),
+        GeometryTypes::LineString => write_line_string(geom, writer),
+        GeometryTypes::Polygon => write_polygon(geom, writer),
+        GeometryTypes::MultiPoint => write_multi_point(geom, writer),
+        GeometryTypes::MultiLineString => write_multi_line_string(geom, 
writer),
+        GeometryTypes::MultiPolygon => write_multi_polygon(geom, writer),
+        GeometryTypes::GeometryCollection => write_geometry_collection(geom, 
writer),
+        _ => Err(DataFusionError::Execution(format!(
+            "Unsupported geometry type: {geom_type:?}"
+        ))),
+    }
+}
+
+fn write_point(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    // Write byte order
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 1,   // Point
+        (true, false) => 1001, // Point Z
+        (false, true) => 2001, // Point M
+        (true, true) => 3001,  // Point ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        // Write NaN coordinates for empty point
+        writer.write_f64::<LittleEndian>(f64::NAN)?; // x
+        writer.write_f64::<LittleEndian>(f64::NAN)?; // y
+        if has_z {
+            writer.write_f64::<LittleEndian>(f64::NAN)?; // z
+        }
+        if has_m {
+            writer.write_f64::<LittleEndian>(f64::NAN)?; // m
+        }
+    } else {
+        let coord_seq = geom
+            .get_coord_seq()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
coord seq: {e}")))?;
+
+        let num_coords = coord_seq.size().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get coord seq size: 
{e}"))
+        })?;
+
+        if num_coords == 0 {
+            return exec_err!("Point has no coordinates");
+        }
+
+        write_coord_seq(&coord_seq, writer, has_z, has_m)?;
+    }
+
+    Ok(())
+}
+
+fn write_line_string(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 2,   // LineString
+        (true, false) => 1002, // LineString Z
+        (false, true) => 2002, // LineString M
+        (true, true) => 3002,  // LineString ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 points
+    } else {
+        let coord_seq = geom
+            .get_coord_seq()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
coord seq: {e}")))?;
+
+        let num_points = coord_seq.size().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get coord seq size: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_points as u32)?;
+
+        write_coord_seq(&coord_seq, writer, has_z, has_m)?;
+    }
+
+    Ok(())
+}
+
+fn write_polygon(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 3,   // Polygon
+        (true, false) => 1003, // Polygon Z
+        (false, true) => 2003, // Polygon M
+        (true, true) => 3003,  // Polygon ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 rings
+    } else {
+        let exterior = geom
+            .get_exterior_ring()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
exterior ring: {e}")))?;
+
+        let exterior_coord_seq = exterior.get_coord_seq().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get exterior coord 
seq: {e}"))
+        })?;
+
+        let num_interior_rings = geom.get_num_interior_rings().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num interior 
rings: {e}"))
+        })?;
+
+        // Number of rings (interior rings + 1 exterior ring)
+        writer.write_u32::<LittleEndian>((num_interior_rings + 1) as u32)?;
+
+        let exterior_size = exterior_coord_seq
+            .size()
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
exterior size: {e}")))?;
+
+        // Number of points in exterior ring
+        writer.write_u32::<LittleEndian>(exterior_size as u32)?;
+        write_coord_seq(&exterior_coord_seq, writer, has_z, has_m)?;
+
+        // Write interior rings
+        for i in 0..num_interior_rings {
+            let interior = geom.get_interior_ring_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
ring {i}: {e}"))
+            })?;
+
+            let interior_coord_seq = interior.get_coord_seq().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
coord seq: {e}"))
+            })?;
+
+            let interior_size = interior_coord_seq.size().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get interior 
size: {e}"))
+            })?;
+
+            writer.write_u32::<LittleEndian>(interior_size as u32)?;
+            write_coord_seq(&interior_coord_seq, writer, has_z, has_m)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_point(geom: &impl Geom, writer: &mut impl Write) -> Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 4,   // MultiPoint
+        (true, false) => 1004, // MultiPoint Z
+        (false, true) => 2004, // MultiPoint M
+        (true, true) => 3004,  // MultiPoint ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 points
+    } else {
+        let num_points = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_points as u32)?;
+
+        for i in 0..num_points {
+            let point = geom
+                .get_geometry_n(i)
+                .map_err(|e| DataFusionError::Execution(format!("Failed to get 
point {i}: {e}")))?;
+
+            write_point(&point, writer)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_line_string(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 5,   // MultiLineString
+        (true, false) => 1005, // MultiLineString Z
+        (false, true) => 2005, // MultiLineString M
+        (true, true) => 3005,  // MultiLineString ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 line strings
+    } else {
+        let num_line_strings = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_line_strings as u32)?;
+
+        for i in 0..num_line_strings {
+            let ls = geom.get_geometry_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get line string 
{i}: {e}"))
+            })?;
+
+            write_line_string(&ls, writer)?;
+        }
+    }
+
+    Ok(())
+}
+
+fn write_multi_polygon(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    let has_z = geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 6,   // MultiPolygon
+        (true, false) => 1006, // MultiPolygon Z
+        (false, true) => 2006, // MultiPolygon M
+        (true, true) => 3006,  // MultiPolygon ZM
+    };
+
+    writer.write_u32::<LittleEndian>(wkb_type)?;
+
+    let is_empty = geom
+        .is_empty()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check if 
empty: {e}")))?;
+
+    if is_empty {
+        writer.write_u32::<LittleEndian>(0)?; // 0 polygons
+    } else {
+        let num_polygons = geom.get_num_geometries().map_err(|e| {
+            DataFusionError::Execution(format!("Failed to get num geometries: 
{e}"))
+        })?;
+
+        writer.write_u32::<LittleEndian>(num_polygons as u32)?;
+
+        for i in 0..num_polygons {
+            let poly = geom.get_geometry_n(i).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get polygon {i}: 
{e}"))
+            })?;
+
+            write_polygon(&poly, writer)?;
+        }
+    }
+    Ok(())
+}
+
+fn write_geometry_collection(geom: &impl Geom, writer: &mut impl Write) -> 
Result<()> {
+    writer.write_u8(NATIVE_ENDIANNESS)?;
+
+    // GeometryCollection's dimension might be specified on the child 
geometries only
+    let dimension = get_geomcol_dimension(geom)?;
+    writer.write_u32::<LittleEndian>(dimension)?;
+
+    let num_geometries = geom
+        .get_num_geometries()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get num 
geometries: {e}")))?;
+
+    writer.write_u32::<LittleEndian>(num_geometries as u32)?;
+
+    for i in 0..num_geometries {
+        let sub_geom = geom
+            .get_geometry_n(i)
+            .map_err(|e| DataFusionError::Execution(format!("Failed to get 
geometry {i}: {e}")))?;
+
+        write_geometry(&sub_geom, writer)?;
+    }
+
+    Ok(())
+}
+
+// TBH. um not sure this is needed for geos
+fn get_geomcol_dimension(geomcol: &impl Geom) -> Result<u32> {
+    let has_z = geomcol
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+
+    let has_m = geomcol
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+
+    let wkb_type = match (has_z, has_m) {
+        (true, false) => Some(1007), // GeometryCollection Z
+        (false, true) => Some(2007), // GeometryCollection M
+        (true, true) => Some(3007),  // GeometryCollection ZM
+        (false, false) => None,      // GeometryCollection
+    };
+
+    // If found non-xy dimension, use it
+    if let Some(wkb_type) = wkb_type {
+        return Ok(wkb_type);
+    }
+
+    // Try inferring from first nested geom
+    let num_geometries = geomcol
+        .get_num_geometries()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get num 
geometries: {e}")))?;
+
+    if num_geometries == 0 {
+        // Guaranteed to be XY only
+        return Ok(7);
+    }
+
+    // Check the first geom's type
+    let sub_geom = geomcol.get_geometry_n(0).map_err(|e| {
+        DataFusionError::Execution(format!("Failed to get first nested 
geometry: {e}"))
+    })?;
+    let sub_geom_type = sub_geom
+        .geometry_type()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get 
geometry type: {e}")))?;
+
+    // If it's a nested geom collection, recurse into that
+    if sub_geom_type == GeometryTypes::GeometryCollection {
+        return get_geomcol_dimension(&sub_geom);
+    }
+
+    let has_z = sub_geom
+        .has_z()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_z: {e}")))?;
+    let has_m = sub_geom
+        .has_m()
+        .map_err(|e| DataFusionError::Execution(format!("Failed to check 
has_m: {e}")))?;
+    let wkb_type = match (has_z, has_m) {
+        (false, false) => 7,   // GeometryCollection
+        (true, false) => 1007, // GeometryCollection Z
+        (false, true) => 2007, // GeometryCollection M
+        (true, true) => 3007,  // GeometryCollection ZM
+    };
+    Ok(wkb_type)
+}
+
+fn write_coord_seq(
+    coord_seq: &geos::CoordSeq,
+    writer: &mut impl Write,
+    has_z: bool,
+    has_m: bool,
+) -> Result<()> {
+    let dims = match (has_z, has_m) {
+        (true, true) => 4,
+        (true, false) | (false, true) => 3,
+        (false, false) => 2,
+    };
+
+    let coords = coord_seq
+        .as_buffer(Some(dims))
+        .map_err(|e| DataFusionError::Execution(format!("Failed to get coord 
seq buffer: {e}")))?;
+
+    // TODO: I guess we could compute the exact size buffer we expect here and 
check it. Should we do it or just assume geos correct?
+    // TODO: do we need to consider endianness??
+
+    // Cast Vec<f64> to &[u8] so we can write the bytes directly to the writer 
buffer
+    let byte_slice: &[u8] = bytemuck::cast_slice(&coords);

Review Comment:
   If we had control over all the parts, the best thing we could possibly do is 
to call `GEOSCoordSeq_copyToBuffer()` on the sequence such that it copies the 
bytes directly into the output buffer ( 
https://github.com/libgeos/geos/blob/158c588566e08fd2f31f8c9e7ae069518e8264c5/capi/geos_c.h.in#L2459-L2469
 ). The second best thing we could do would be to keep a mutable `Vec<f64>` on 
hand that we re-use every time to copy the sequence into, then write the bytes 
into the output. Given the constraints of the current `as_buffer()` I think 
your solution is the best we can do for now!
   
   As a side note, there's a possibly a bug in `as_buffer()` (the logic won't 
work for XYM geometries): 
https://github.com/georust/geos/blob/47afbad2483e489911ddb456417808340e9342c3/src/coord_seq.rs#L521-L540
 .



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