WIP: implement ops for st_buffer, st_centroid, and st_convexhull

Author: tswast

bigframes/bigquery/__init__.py

@@ -29,6 +29,9 @@
 )
 from bigframes.bigquery._operations.geo import (
     st_area,
+    st_buffer,
+    st_centroid,
+    st_convex_hull,
     st_difference,
     st_distance,
     st_intersection,
@@ -59,6 +62,9 @@
     "array_to_string",
     # geo ops
     "st_area",
+    "st_buffer",
+    "st_centroid",
+    "st_convex_hull",
     "st_difference",
     "st_distance",
     "st_intersection",

bigframes/core/compile/scalar_op_compiler.py

@@ -1038,6 +1038,21 @@ def geo_st_boundary_op_impl(x: ibis_types.Value):
     return st_boundary(x)
 
 
+@scalar_op_compiler.register_unary_op(ops.GeoStBufferOp, pass_op=True)
+def geo_st_buffer_op_impl(x: ibis_types.Value, op: ops.GeoStBufferOp):
+    return typing.cast(ibis_types.GeoSpatialValue, x).buffer(op.distance)
+
+
+@scalar_op_compiler.register_unary_op(ops.geo_st_centroid_op, pass_op=False)
+def geo_st_centroid_op_impl(x: ibis_types.Value):
+    return typing.cast(ibis_types.GeoSpatialValue, x).centroid()
+
+
+@scalar_op_compiler.register_unary_op(ops.geo_st_convexhull_op, pass_op=False)
+def geo_st_convexhull_op_impl(x: ibis_types.Value):
+    return typing.cast(ibis_types.GeoSpatialValue, x).convex_hull()
+
+
 @scalar_op_compiler.register_binary_op(ops.geo_st_difference_op, pass_op=False)
 def geo_st_difference_op_impl(x: ibis_types.Value, y: ibis_types.Value):
     return typing.cast(ibis_types.GeoSpatialValue, x).difference(

bigframes/geopandas/geoseries.py

@@ -92,6 +92,15 @@ def to_wkt(self: GeoSeries) -> bigframes.series.Series:
         series.name = None
         return series
 
+    def buffer(self: GeoSeries, distance: float) -> bigframes.series.Series:  # type: ignore
+        return self._apply_unary_op(ops.GeoStBufferOp(distance=distance))
+
+    def centroid(self: GeoSeries) -> bigframes.series.Series:  # type: ignore
+        return self._apply_unary_op(ops.geo_st_centroid_op)
+
+    def convex_hull(self: GeoSeries) -> bigframes.series.Series:  # type: ignore
+        return self._apply_unary_op(ops.geo_st_convexhull_op)
+
     def difference(self: GeoSeries, other: GeoSeries) -> bigframes.series.Series:  # type: ignore
         return self._apply_binary_op(other, ops.geo_st_difference_op)
 

bigframes/operations/geo_ops.py

@@ -42,6 +42,22 @@
 )
 geo_st_boundary_op = GeoStBoundaryOp()
 
+GeoStCentroidOp = base_ops.create_unary_op(
+    name="geo_st_centroid",
+    type_signature=op_typing.FixedOutputType(
+        dtypes.is_geo_like, dtypes.GEO_DTYPE, description="geo-like"
+    ),
+)
+geo_st_centroid_op = GeoStCentroidOp()
+
+GeoStConvexhullOp = base_ops.create_unary_op(
+    name="geo_st_convexhull",
+    type_signature=op_typing.FixedOutputType(
+        dtypes.is_geo_like, dtypes.GEO_DTYPE, description="geo-like"
+    ),
+)
+geo_st_convexhull_op = GeoStConvexhullOp()
+
 GeoStDifferenceOp = base_ops.create_binary_op(
     name="geo_st_difference", type_signature=op_typing.BinaryGeo()
 )
@@ -90,6 +106,15 @@
 geo_st_intersection_op = GeoStIntersectionOp()
 
 
+@dataclasses.dataclass(frozen=True)
+class GeoStBufferOp(base_ops.UnaryOp):
+    name = "st_buffer"
+    distance: float
+
+    def output_type(self, *input_types: dtypes.ExpressionType) -> dtypes.ExpressionType:
+        return dtypes.GEO_DTYPE
+
+
 @dataclasses.dataclass(frozen=True)
 class GeoStDistanceOp(base_ops.BinaryOp):
     name = "st_distance"

specs/2025-08-04-geoseries-scalars.md

@@ -79,9 +79,9 @@ functions should be exposed in the `bigframes.bigquery` module.
 - [ ] GeoSeries.symmetric_difference
 - [ ] GeoSeries.union
 - [x] GeoSeries.boundary
-- [ ] GeoSeries.buffer
-- [ ] GeoSeries.centroid
-- [ ] GeoSeries.concave_hull
+- [WIP] GeoSeries.buffer
+- [WIP] GeoSeries.centroid
+- [WIP] GeoSeries.concave_hull
 - [ ] GeoSeries.convex_hull
 - [ ] GeoSeries.envelope
 - [ ] GeoSeries.extract_unique_points
@@ -174,12 +174,12 @@ Formatters: Functions that export geographies to an external format such as WKT.
 Transformations: Functions that generate a new geography based on input.
 
 - [x] ST_BOUNDARY
-- [ ] ST_BUFFER
+- [WIP] ST_BUFFER
 - [ ] ST_BUFFERWITHTOLERANCE
-- [ ] ST_CENTROID
+- [WIP] ST_CENTROID
 - [ ] ST_CENTROID_AGG (Aggregate)
 - [ ] ST_CLOSESTPOINT
-- [ ] ST_CONVEXHULL
+- [WIP] ST_CONVEXHULL
 - [x] ST_DIFFERENCE
 - [ ] ST_EXTERIORRING
 - [ ] ST_INTERIORRINGS