fix

crates/polars-arrow/src/mmap/array.rs

@@ -139,22 +139,23 @@ fn mmap_binview<T: AsRef<[u8]>>(
 
     let validity = get_validity(data_ref, block_offset, buffers, null_count)?.map(|x| x.as_ptr());
 
-    let views = get_buffer::<u128>(data_ref, block_offset, buffers, num_rows)?.as_ptr();
+    let views = get_buffer::<u128>(data_ref, block_offset, buffers, num_rows)?;
 
     let n_variadic = variadic_buffer_counts
         .pop_front()
         .ok_or_else(|| polars_err!(ComputeError: "expected variadic_buffer_count"))?;
 
     let mut buffer_ptrs = Vec::with_capacity(n_variadic + 2);
     buffer_ptrs.push(validity);
-    buffer_ptrs.push(Some(views));
+    buffer_ptrs.push(Some(views.as_ptr()));
 
     let mut variadic_buffer_sizes = Vec::with_capacity(n_variadic);
     for _ in 0..n_variadic {
         let variadic_buffer = get_bytes(data_ref, block_offset, buffers)?;
-        variadic_buffer_sizes.push(variadic_buffer.len());
+        variadic_buffer_sizes.push(variadic_buffer.len() as i64);
         buffer_ptrs.push(Some(variadic_buffer.as_ptr()));
     }
+    buffer_ptrs.push(Some(variadic_buffer_sizes.as_ptr().cast::<u8>()));
 
     // Move variadic buffer sizes in an Arc, so that it stays alive.
     let data = Arc::new((data, variadic_buffer_sizes));

py-polars/polars/dataframe/frame.py

@@ -3255,6 +3255,8 @@ def write_ipc(
         self,
         file: None,
         compression: IpcCompression = "uncompressed",
+        *,
+        future: bool = False,
     ) -> BytesIO:
         ...
 
@@ -3263,13 +3265,17 @@ def write_ipc(
         self,
         file: BinaryIO | BytesIO | str | Path,
         compression: IpcCompression = "uncompressed",
+        *,
+        future: bool = False,
     ) -> None:
         ...
 
     def write_ipc(
         self,
         file: BinaryIO | BytesIO | str | Path | None,
         compression: IpcCompression = "uncompressed",
+        *,
+        future: bool = False,
     ) -> BytesIO | None:
         """
         Write to Arrow IPC binary stream or Feather file.
@@ -3283,6 +3289,11 @@ def write_ipc(
             written. If set to `None`, the output is returned as a BytesIO object.
         compression : {'uncompressed', 'lz4', 'zstd'}
             Compression method. Defaults to "uncompressed".
+        future
+            WARNING: this argument is unstable and will be removed without it being
+            considered a breaking change.
+            Setting this to `True` will write polars' internal data-structures that
+            might not be available by other Arrow implementations.
 
         Examples
         --------
@@ -3307,7 +3318,7 @@ def write_ipc(
         if compression is None:
             compression = "uncompressed"
 
-        self._df.write_ipc(file, compression)
+        self._df.write_ipc(file, compression, future)
         return file if return_bytes else None  # type: ignore[return-value]
 
     @overload

py-polars/src/dataframe.rs

@@ -665,12 +665,14 @@ impl PyDataFrame {
         py: Python,
         py_f: PyObject,
         compression: Wrap<Option<IpcCompression>>,
+        future: bool,
     ) -> PyResult<()> {
         if let Ok(s) = py_f.extract::<&str>(py) {
             let f = std::fs::File::create(s)?;
             py.allow_threads(|| {
                 IpcWriter::new(f)
                     .with_compression(compression.0)
+                    .with_pl_flavor(future)
                     .finish(&mut self.df)
                     .map_err(PyPolarsErr::from)
             })?;
@@ -679,6 +681,7 @@ impl PyDataFrame {
 
             IpcWriter::new(&mut buf)
                 .with_compression(compression.0)
+                .with_pl_flavor(future)
                 .finish(&mut self.df)
                 .map_err(PyPolarsErr::from)?;
         }

py-polars/tests/unit/io/test_ipc.py

@@ -188,7 +188,6 @@ def test_ipc_column_order(stream: bool) -> None:
 
 @pytest.mark.write_disk()
 def test_glob_ipc(df: pl.DataFrame, tmp_path: Path) -> None:
-    tmp_path.mkdir(exist_ok=True)
     file_path = tmp_path / "small.ipc"
     df.write_ipc(file_path)
 
@@ -208,3 +207,12 @@ def test_from_float16() -> None:
     pandas_df.to_feather(f)
     f.seek(0)
     assert pl.read_ipc(f, use_pyarrow=False).dtypes == [pl.Float32]
+
+
+@pytest.mark.write_disk()
+def test_binview_ipc_mmap(tmp_path: Path) -> None:
+    df = pl.DataFrame({"foo": ["aa" * 10, "bb", None, "small", "big" * 20]})
+    file_path = tmp_path / "dump.ipc"
+    df.write_ipc(file_path, future=True)
+    read = pl.read_ipc(file_path, memory_map=True)
+    assert_frame_equal(df, read)