negative slice fix

pola-rs · Mar 3, 2025 · 50b907c · 50b907c
1 parent 965d996
commit 50b907c
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Showing 2 changed files with 9 additions and 2 deletions.
diff --git a/crates/polars-stream/src/nodes/negative_slice.rs b/crates/polars-stream/src/nodes/negative_slice.rs
@@ -72,8 +72,9 @@ impl ComputeNode for NegativeSliceNode {
                     signed_start_offset -= len as i64;
                 }
 
-                while buffer.total_len as i64 - buffer.frames.back().unwrap().height() as i64
-                    > signed_stop_offset
+                while !buffer.frames.is_empty()
+                    && buffer.total_len as i64 - buffer.frames.back().unwrap().height() as i64
+                        > signed_stop_offset
                 {
                     buffer.total_len -= buffer.frames.pop_back().unwrap().height();
                 }

diff --git a/py-polars/tests/unit/operations/test_slice.py b/py-polars/tests/unit/operations/test_slice.py
@@ -310,3 +310,9 @@ def test_slice_pushdown_panic_20216() -> None:
 
     assert_frame_equal(q.slice(0, 1).collect(), pl.DataFrame({"A": ["1"]}))
     assert_frame_equal(q.collect(), pl.DataFrame({"A": ["1"]}))
+
+
+def test_slice_empty_morsel_input() -> None:
+    q = pl.LazyFrame({"a": []})
+    assert_frame_equal(q.slice(999, 3).slice(999, 3).collect(), q.collect().clear())
+    assert_frame_equal(q.slice(-999, 3).slice(-999, 3).collect(), q.collect().clear())