From 66b17e939e3629b6f36471d10e18675891d53b82 Mon Sep 17 00:00:00 2001
From: Marco Gorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Wed, 8 Jan 2025 13:55:20 +0000
Subject: [PATCH] fixup

---
 narwhals/_duckdb/expr.py               | 24 ++++++++++++++++++++++++
 tests/expr_and_series/n_unique_test.py |  6 +-----
 tests/expr_and_series/unary_test.py    |  6 +-----
 tests/group_by_test.py                 |  8 +-------
 tpch/execute.py                        |  2 +-
 5 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/narwhals/_duckdb/expr.py b/narwhals/_duckdb/expr.py
index 4515cbba1..297d9e64a 100644
--- a/narwhals/_duckdb/expr.py
+++ b/narwhals/_duckdb/expr.py
@@ -408,6 +408,30 @@ def sum(self) -> Self:
             lambda _input: FunctionExpression("sum", _input), "sum", returns_scalar=True
         )
 
+    def n_unique(self) -> Self:
+        from duckdb import CaseExpression
+        from duckdb import ConstantExpression
+        from duckdb import FunctionExpression
+
+        def func(_input: duckdb.Expression) -> duckdb.Expression:
+            return (
+                FunctionExpression(
+                    "array_unique", FunctionExpression("array_agg", _input)
+                )
+                + FunctionExpression(
+                    "max",
+                    CaseExpression(
+                        condition=_input.isnotnull(), value=ConstantExpression(0)
+                    ).otherwise(ConstantExpression(1)),
+                )
+            ).alias("result")
+
+        return self._from_call(
+            func,
+            "n_unique",
+            returns_scalar=True,
+        )
+
     def count(self) -> Self:
         from duckdb import FunctionExpression
 
diff --git a/tests/expr_and_series/n_unique_test.py b/tests/expr_and_series/n_unique_test.py
index d8e4d9b77..90bffb04b 100644
--- a/tests/expr_and_series/n_unique_test.py
+++ b/tests/expr_and_series/n_unique_test.py
@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-import pytest
-
 import narwhals.stable.v1 as nw
 from tests.utils import Constructor
 from tests.utils import ConstructorEager
@@ -13,9 +11,7 @@
 }
 
 
-def test_n_unique(constructor: Constructor, request: pytest.FixtureRequest) -> None:
-    if "duckdb" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
+def test_n_unique(constructor: Constructor) -> None:
     df = nw.from_native(constructor(data))
     result = df.select(nw.all().n_unique())
     expected = {"a": [3], "b": [4]}
diff --git a/tests/expr_and_series/unary_test.py b/tests/expr_and_series/unary_test.py
index 9ee38a230..f3e01d80f 100644
--- a/tests/expr_and_series/unary_test.py
+++ b/tests/expr_and_series/unary_test.py
@@ -126,11 +126,7 @@ def test_unary_two_elements_series(constructor_eager: ConstructorEager) -> None:
     assert_equal_data(result, expected)
 
 
-def test_unary_one_element(
-    constructor: Constructor, request: pytest.FixtureRequest
-) -> None:
-    if "duckdb" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
+def test_unary_one_element(constructor: Constructor) -> None:
     data = {"a": [1], "b": [2], "c": [None]}
     # Dask runs into a divide by zero RuntimeWarning for 1 element skew.
     context = (
diff --git a/tests/group_by_test.py b/tests/group_by_test.py
index 0dd6d8a10..c854da453 100644
--- a/tests/group_by_test.py
+++ b/tests/group_by_test.py
@@ -115,8 +115,6 @@ def test_group_by_depth_1_agg(
     expected: dict[str, list[int | float]],
     request: pytest.FixtureRequest,
 ) -> None:
-    if "duckdb" in str(constructor) and attr == "n_unique":
-        request.applymarker(pytest.mark.xfail)
     if "pandas_pyarrow" in str(constructor) and attr == "var" and PANDAS_VERSION < (2, 1):
         # Known issue with variance calculation in pandas 2.0.x with pyarrow backend in groupby operations"
         request.applymarker(pytest.mark.xfail)
@@ -166,11 +164,7 @@ def test_group_by_median(constructor: Constructor) -> None:
     assert_equal_data(result, expected)
 
 
-def test_group_by_n_unique_w_missing(
-    constructor: Constructor, request: pytest.FixtureRequest
-) -> None:
-    if "duckdb" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
+def test_group_by_n_unique_w_missing(constructor: Constructor) -> None:
     data = {"a": [1, 1, 2], "b": [4, None, 5], "c": [None, None, 7], "d": [1, 1, 3]}
     result = (
         nw.from_native(constructor(data))
diff --git a/tpch/execute.py b/tpch/execute.py
index 1f3823ced..f2f3041df 100644
--- a/tpch/execute.py
+++ b/tpch/execute.py
@@ -40,7 +40,7 @@
     "dask": lambda x: x.compute(),
 }
 
-DUCKDB_XFAILS = ["q11", "q14", "q15", "q16", "q18", "q22"]
+DUCKDB_XFAILS = ["q11", "q14", "q15", "q18", "q22"]
 
 QUERY_DATA_PATH_MAP = {
     "q1": (LINEITEM_PATH,),