feat(duckdb): enforce aswkb for projections, coerce to geopandas

Two things happening in here:
1. We intercept the call to `get_sqla_type` to enforce the use of
`ST_AsWKB`, overriding the behavior of `geoalchemy` which is very
PostGIS-focused.
2. We add a DuckDB-specific `_to_geodataframe` since we're getting a WKB
out of DuckDB and can pass this directly to `geopandas` without first
going through Shapely (as we do in the base alchemy method)

Author: gforsyth

ibis/backends/duckdb/__init__.py

@@ -24,6 +24,7 @@
 from ibis import util
 from ibis.backends.base import CanCreateSchema
 from ibis.backends.base.sql.alchemy import AlchemyCrossSchemaBackend
+from ibis.backends.base.sql.alchemy.geospatial import geospatial_supported
 from ibis.backends.base.sqlglot import C, F
 from ibis.backends.duckdb.compiler import DuckDBSQLCompiler
 from ibis.backends.duckdb.datatypes import DuckDBType
@@ -1199,7 +1200,30 @@ def fetch_from_cursor(
                 for name, col in zip(table.column_names, table.columns)
             }
         )
-        return PandasData.convert_table(df, schema)
+        df = PandasData.convert_table(df, schema)
+        if not df.empty and geospatial_supported:
+            return self._to_geodataframe(df, schema)
+        return df
+
+    # TODO(gforsyth): this may not need to be specialized in the future
+    @staticmethod
+    def _to_geodataframe(df, schema):
+        """Convert `df` to a `GeoDataFrame`.
+
+        Required libraries for geospatial support must be installed and
+        a geospatial column is present in the dataframe.
+        """
+        import geopandas as gpd
+
+        geom_col = None
+        for name, dtype in schema.items():
+            if dtype.is_geospatial():
+                if not geom_col:
+                    geom_col = name
+                df[name] = gpd.GeoSeries.from_wkb(df[name])
+        if geom_col:
+            df = gpd.GeoDataFrame(df, geometry=geom_col)
+        return df
 
     def _metadata(self, query: str) -> Iterator[tuple[str, dt.DataType]]:
         with self.begin() as con:

ibis/backends/duckdb/datatypes.py

@@ -7,6 +7,19 @@
 from ibis.backends.base.sql.alchemy.datatypes import AlchemyType
 from ibis.backends.base.sqlglot.datatypes import DuckDBType as SqlglotDuckdbType
 
+
+try:
+    from geoalchemy2 import Geometry
+
+    class Geometry_WKB(Geometry):
+        as_binary = "ST_AsWKB"
+
+except ImportError:
+
+    class Geometry_WKB:
+        ...
+
+
 _from_duckdb_types = {
     psql.BYTEA: dt.Binary,
     psql.UUID: dt.UUID,
@@ -35,6 +48,8 @@
     dt.UInt16: ducktypes.USmallInteger,
     dt.UInt32: ducktypes.UInteger,
     dt.UInt64: ducktypes.UBigInteger,
+    # Handle projections with geometry columns
+    dt.Geometry: Geometry_WKB,
 }
 
 

ibis/backends/duckdb/tests/test_register.py

@@ -46,14 +46,22 @@ def test_read_parquet(data_dir):
     assert t.count().execute()
 
 
-@pytest.mark.xfail(raises=duckdb.duckdb.CatalogException, reason="ST_AsEWKB")
-def test_read_geo_fail(con, data_dir):
+@pytest.mark.xfail(raises=NotImplementedError)
+def test_read_geo_to_pyarrow(con, data_dir):
     pytest.importorskip("geopandas")
     t = con.read_geo(data_dir / "geojson" / "zones.geojson")
     # can't convert geometry to arrow type yet
     assert t.head().to_pyarrow()
 
 
+def test_read_geo_to_geopandas(con, data_dir):
+    gpd = pytest.importorskip("geopandas")
+    t = con.read_geo(data_dir / "geojson" / "zones.geojson")
+    # can't convert geometry to arrow type yet
+    gdf = t.head().to_pandas()
+    assert isinstance(gdf, gpd.GeoDataFrame)
+
+
 def test_read_geo(con, data_dir):
     pytest.importorskip("geopandas")
     t = con.read_geo(data_dir / "geojson" / "zones.geojson")