feat: add DuckDB Struct dtype (#1851)

narwhals-dev · Jan 22, 2025 · 38e5261 · 38e5261
1 parent 07e8024
commit 38e5261
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Showing 2 changed files with 11 additions and 9 deletions.
diff --git a/narwhals/_duckdb/utils.py b/narwhals/_duckdb/utils.py
@@ -157,9 +157,9 @@ def native_to_narwhals_dtype(duckdb_dtype: str, version: Version) -> DType:
 def narwhals_to_native_dtype(dtype: DType | type[DType], version: Version) -> str:
     dtypes = import_dtypes_module(version)
     if isinstance_or_issubclass(dtype, dtypes.Float64):
-        return "FLOAT"
-    if isinstance_or_issubclass(dtype, dtypes.Float32):
         return "DOUBLE"
+    if isinstance_or_issubclass(dtype, dtypes.Float32):
+        return "FLOAT"
     if isinstance_or_issubclass(dtype, dtypes.Int64):
         return "BIGINT"
     if isinstance_or_issubclass(dtype, dtypes.Int32):
@@ -198,8 +198,11 @@ def narwhals_to_native_dtype(dtype: DType | type[DType], version: Version) -> st
         inner = narwhals_to_native_dtype(dtype.inner, version)  # type: ignore[union-attr]
         return f"{inner}[]"
     if isinstance_or_issubclass(dtype, dtypes.Struct):  # pragma: no cover
-        msg = "todo"
-        raise NotImplementedError(msg)
+        inner = ", ".join(
+            f'"{field.name}" {narwhals_to_native_dtype(field.dtype, version)}'
+            for field in dtype.fields  # type: ignore[union-attr]
+        )
+        return f"STRUCT({inner})"
     if isinstance_or_issubclass(dtype, dtypes.Array):  # pragma: no cover
         msg = "todo"
         raise NotImplementedError(msg)

diff --git a/tests/expr_and_series/cast_test.py b/tests/expr_and_series/cast_test.py
@@ -236,8 +236,7 @@ def test_cast_datetime_tz_aware(
 
 def test_cast_struct(request: pytest.FixtureRequest, constructor: Constructor) -> None:
     if any(
-        backend in str(constructor)
-        for backend in ("dask", "modin", "cudf", "duckdb", "pyspark")
+        backend in str(constructor) for backend in ("dask", "modin", "cudf", "pyspark")
     ):
         request.applymarker(pytest.mark.xfail)
 
@@ -246,12 +245,12 @@ def test_cast_struct(request: pytest.FixtureRequest, constructor: Constructor) -
 
     data = {
         "a": [
-            {"movie": "Cars", "rating": 4.5},
-            {"movie": "Toy Story", "rating": 4.9},
+            {"movie ": "Cars", "rating": 4.5},
+            {"movie ": "Toy Story", "rating": 4.9},
         ]
     }
 
-    dtype = nw.Struct([nw.Field("movie", nw.String()), nw.Field("rating", nw.Float64())])
+    dtype = nw.Struct([nw.Field("movie ", nw.String()), nw.Field("rating", nw.Float64())])
     result = (
         nw.from_native(constructor(data)).select(nw.col("a").cast(dtype)).lazy().collect()
     )