use first series to validate length (#3551)

pola-rs · Jun 1, 2022 · 5b23e4e · 5b23e4e
1 parent de92284
commit 5b23e4e
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/polars/polars-lazy/src/physical_plan/expressions/apply.rs b/polars/polars-lazy/src/physical_plan/expressions/apply.rs
@@ -189,7 +189,7 @@ impl PhysicalExpr for ApplyExpr {
                         })
                         .collect::<Vec<_>>();
 
-                    let input_len = s.iter().map(|s| s.len()).max().unwrap();
+                    let input_len = s[0].len();
                     let s = self.function.call_udf(&mut s)?;
                     check_map_output_len(input_len, s.len())?;
 

diff --git a/polars/tests/it/lazy/expressions/window.rs b/polars/tests/it/lazy/expressions/window.rs
@@ -385,3 +385,18 @@ fn test_window_naive_any() -> Result<()> {
     assert_eq!(res.sum::<usize>(), Some(5));
     Ok(())
 }
+
+#[test]
+fn test_window_map_empty_df_3542() -> Result<()> {
+    let df = df![
+        "x" => ["a", "b", "c"],
+        "y" => [Some(1), None, Some(3)]
+    ]?;
+    let out = df
+        .lazy()
+        .filter(col("y").lt(0))
+        .select([col("y").fill_null(0).last().over([col("y")])])
+        .collect()?;
+    assert_eq!(out.height(), 0);
+    Ok(())
+}