fix: Fix right join schema (#17833)

crates/polars-plan/src/plans/schema.rs

@@ -249,7 +249,7 @@ pub(crate) fn det_join_schema(
             let mut arena = Arena::with_capacity(8);
             let mut join_on_left: PlHashSet<_> = PlHashSet::with_capacity(left_on.len());
             for e in left_on {
-                let field = e.to_field_amortized(schema_right, Context::Default, &mut arena)?;
+                let field = e.to_field_amortized(schema_left, Context::Default, &mut arena)?;
                 join_on_left.insert(field.name);
             }
 

py-polars/tests/unit/operations/test_join_right.py

@@ -71,3 +71,27 @@ def test_right_join_schemas_multikey() -> None:
     assert b.join(a, on=["a", "b"], how="right", coalesce=True).to_dict(
         as_series=False
     ) == {"c": [1, None, 3], "a": [1, 2, 3], "b": [1, 2, 3], "c_right": [1, 2, 3]}
+
+
+def test_join_right_different_key() -> None:
+    df = pl.DataFrame(
+        {
+            "foo": [1, 2, 3],
+            "bar": [6.0, 7.0, 8.0],
+            "ham1": ["a", "b", "c"],
+        }
+    )
+    other_df = pl.DataFrame(
+        {
+            "apple": ["x", "y", "z"],
+            "ham2": ["a", "b", "d"],
+        }
+    )
+    assert df.join(other_df, left_on="ham1", right_on="ham2", how="right").to_dict(
+        as_series=False
+    ) == {
+        "foo": [1, 2, None],
+        "bar": [6.0, 7.0, None],
+        "apple": ["x", "y", "z"],
+        "ham2": ["a", "b", "d"],
+    }