test: add buffer implementation and mark broken

ibis/backends/duckdb/registry.py

@@ -87,6 +87,12 @@ def _envelope(t, op):
     return sa.func.st_envelope(arg, type_=Geometry_WKB)
 
 
+def _geo_buffer(t, op):
+    arg = t.translate(op.arg)
+    radius = t.translate(op.radius)
+    return sa.func.st_buffer(arg, radius, type_=Geometry_WKB)
+
+
 def _geo_unary_union(t, op):
     arg = t.translate(op.arg)
     return sa.func.st_union_agg(arg, type_=Geometry_WKB)
@@ -562,7 +568,8 @@ def _to_json_collection(t, op):
         ops.GeoPoint: _geo_point,
         ops.GeoAsText: unary(sa.func.ST_AsText),
         ops.GeoArea: unary(sa.func.ST_Area),
-        # ops.GeoBuffer: fixed_arity(sa.func.ST_Buffer, 2), duckdb sup 2 or 3?
+        # ops.GeoBuffer: fixed_arity(sa.func.ST_Buffer, 2),
+        ops.GeoBuffer: _geo_buffer,
         # ops.GeoCentroid: unary(sa.func.ST_Centroid),
         ops.GeoCentroid: _centroid,
         ops.GeoContains: fixed_arity(sa.func.ST_Contains, 2),

ibis/backends/duckdb/tests/test_geospatial.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import geopandas as gpd
+import geopandas.testing as gtm
 import numpy.testing as npt
 import pandas.testing as tm
 import pyarrow as pa
@@ -231,12 +232,6 @@ def test_geospatial_y(zones, zones_gdf):
     tm.assert_series_equal(y.to_pandas(), gp_cen.y, check_names=False)
 
 
-# def test_geospatial_buffer()
-# GeoBUffer in alchemy supports 2 arguments, but duckdb is a unary?
-# actually docs are wrong, it takes 2 or 3 args
-# looks like we have fixed_arity(sa.func.ST_Buffer, 2)
-
-
 @pytest.mark.broken(["duckdb"], raises=AssertionError, reason="no match with geopandas")
 def test_geospatial_unary_union(zones, zones_gdf):
     unary_union = zones.geom.unary_union().name("unary_union")
@@ -245,3 +240,46 @@ def test_geospatial_unary_union(zones, zones_gdf):
 
     # we should try to use equals_exact but not even equals pass
     assert shapely.equals(shapely.from_wkb(unary_union.to_pandas()), gp_unary_union)
+
+
+def test_geospatial_buffer_point(zones, zones_gdf):
+    # when we add a buffer to a single point things work
+    cen = zones.geom.centroid().name("centroid")
+    gp_cen = zones_gdf.geometry.centroid
+
+    buffer = cen.buffer(100.0)
+    # geopandas resolution default is 16, while duckdb is 8.
+    gp_buffer = gp_cen.buffer(100.0, resolution=8)
+
+    gtm.assert_geoseries_equal(
+        gpd.GeoSeries.from_wkb(buffer.to_pandas().values), gp_buffer, check_crs=False
+    )
+
+    # check areas are the same
+    tm.assert_series_equal(buffer.area().to_pandas(), gp_buffer.area, check_names=False)
+
+
+@pytest.mark.broken(["duckdb"], raises=AssertionError, reason="no match with geopandas")
+def test_geospatial_buffer(zones, zones_gdf):
+    # When generating buffer from a more complex geometry, we get a match on the geometry
+    # but errors in the area for ~7% of the series.
+
+    buffer = zones.geom.buffer(100.0)
+    # geopandas resolution default is 16, while duckdb is 8.
+    gp_buffer = zones_gdf.geometry.buffer(100.0, resolution=8)
+
+    # comparing the geometries directly  works
+    gtm.assert_geoseries_equal(
+        gpd.GeoSeries.from_wkb(buffer.to_pandas().values), gp_buffer, check_crs=False
+    )
+
+    # when we check the area we have problems
+    # Notice that buffer.area().to_pandas() != gpd.GeoSeries.from_wkb(buffer.to_pandas().values).area
+    # Not clear which area is the correct one, geopandas in their area docs says
+    # Area may be invalid for a geographic CRS using degrees as units;
+    # use GeoSeries.to_crs() to project geometries to a planar CRS before using this function.
+    # gp_buffere.crs says axis info is ellipsoidal. But it is not clear how to project in this case
+    # when trying to_crs() with different epsg, I always get inf.
+    tm.assert_series_equal(
+        buffer.area().to_pandas(), gp_buffer.area, check_names=False, check_exact=False
+    )