fix: Incorrect Decimal value for fill_null(strategy="one") (pola-…

…rs#20844)
alexander-beedie · Jan 22, 2025 · 24fccc4 · 24fccc4
1 parent f79ea83
commit 24fccc4
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 0 deletions.
diff --git a/crates/polars-core/src/chunked_array/ops/fill_null.rs b/crates/polars-core/src/chunked_array/ops/fill_null.rs
@@ -93,6 +93,15 @@ impl Series {
                 fill_backward_gather(self)
             },
             FillNullStrategy::Backward(Some(limit)) => fill_backward_gather_limit(self, limit),
+            #[cfg(feature = "dtype-decimal")]
+            FillNullStrategy::One if self.dtype().is_decimal() => {
+                let ca = self.decimal().unwrap();
+                let precision = ca.precision();
+                let scale = ca.scale();
+                let fill_value = 10i128.pow(scale as u32);
+                let phys = ca.as_ref().fill_null_with_values(fill_value)?;
+                Ok(phys.into_decimal_unchecked(precision, scale).into_series())
+            },
             _ => {
                 let logical_type = self.dtype();
                 let s = self.to_physical_repr();

diff --git a/py-polars/tests/unit/datatypes/test_decimal.py b/py-polars/tests/unit/datatypes/test_decimal.py
@@ -638,3 +638,16 @@ def test_shift_over_12957() -> None:
     )
     assert result["x"].to_list() == [None, D("1.1"), None, D("2.2")]
     assert result["y"].to_list() == [None, 1, None, 2]
+
+
+def test_fill_null() -> None:
+    s = pl.Series("a", [D("1.2"), None, D("1.4")])
+
+    assert s.fill_null(D("0.0")).to_list() == [D("1.2"), D("0.0"), D("1.4")]
+    assert s.fill_null(strategy="zero").to_list() == [D("1.2"), D("0.0"), D("1.4")]
+    assert s.fill_null(strategy="max").to_list() == [D("1.2"), D("1.4"), D("1.4")]
+    assert s.fill_null(strategy="min").to_list() == [D("1.2"), D("1.2"), D("1.4")]
+    assert s.fill_null(strategy="one").to_list() == [D("1.2"), D("1.0"), D("1.4")]
+    assert s.fill_null(strategy="forward").to_list() == [D("1.2"), D("1.2"), D("1.4")]
+    assert s.fill_null(strategy="backward").to_list() == [D("1.2"), D("1.4"), D("1.4")]
+    assert s.fill_null(strategy="mean").to_list() == [D("1.2"), D("1.3"), D("1.4")]