fix: Empty unique (#16214)

pola-rs · May 14, 2024 · 993cc99 · 993cc99
1 parent e3c338a
commit 993cc99
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Showing 2 changed files with 12 additions and 5 deletions.
diff --git a/crates/polars-lazy/src/physical_plan/executors/unique.rs b/crates/polars-lazy/src/physical_plan/executors/unique.rs
@@ -19,9 +19,15 @@ impl Executor for UniqueExec {
         let keep = self.options.keep_strategy;
 
         state.record(
-            || match self.options.maintain_order {
-                true => df.unique_stable(subset, keep, self.options.slice),
-                false => df.unique(subset, keep, self.options.slice),
+            || {
+                if df.height() == 0 {
+                    return Ok(df);
+                }
+
+                match self.options.maintain_order {
+                    true => df.unique_stable(subset, keep, self.options.slice),
+                    false => df.unique(subset, keep, self.options.slice),
+                }
             },
             Cow::Borrowed("unique()"),
         )

diff --git a/py-polars/tests/unit/test_empty.py b/py-polars/tests/unit/test_empty.py
@@ -135,5 +135,6 @@ def test_empty_is_in() -> None:
     )
 
 
-def test_empty_to_empty() -> None:
-    assert pl.DataFrame().drop_nulls().shape == (0, 0)
+@pytest.mark.parametrize("method", ["drop_nulls", "unique"])
+def test_empty_to_empty(method: str) -> None:
+    assert getattr(pl.DataFrame(), method)().shape == (0, 0)