feat: support arrow pycapsule streams

pyiceberg/io/pyarrow.py

@@ -149,7 +149,7 @@
 from pyiceberg.table.name_mapping import NameMapping, apply_name_mapping
 from pyiceberg.table.puffin import PuffinFile
 from pyiceberg.transforms import IdentityTransform, TruncateTransform
-from pyiceberg.typedef import EMPTY_DICT, Properties, Record, TableVersion
+from pyiceberg.typedef import EMPTY_DICT, ArrowStreamExportable, Properties, Record, TableVersion
 from pyiceberg.types import (
     BinaryType,
     BooleanType,
@@ -2680,30 +2680,45 @@ def bin_pack_arrow_table(tbl: pa.Table, target_file_size: int) -> Iterator[list[
     """Bin-pack ``tbl`` into groups of RecordBatches, each ~``target_file_size``.
 
     Note:
-        ``target_file_size`` is measured in **uncompressed in-memory** Arrow bytes
-        (``Table.nbytes`` / ``RecordBatch.nbytes``), not compressed on-disk Parquet
-        bytes. The resulting Parquet file after compression (zstd by default,
-        plus dictionary/RLE encoding) is typically 3-10× smaller than
-        ``target_file_size``. This is a coarse proxy for the spec-defined
+        ``target_file_size`` is measured in **uncompressed in-memory** Arrow
+        bytes, not compressed on-disk Parquet bytes. The size estimate uses
+        ``nbytes`` when available and falls back to referenced buffer size for
+        Arrow view types that do not support ``nbytes``. The resulting Parquet
+        file after compression (zstd by default, plus dictionary/RLE encoding)
+        is typically 3-10× smaller than ``target_file_size``. This is a coarse
+        proxy for the spec-defined
         ``write.target-file-size-bytes`` and will be tightened to true on-disk
         bytes once the writer is switched to a rolling-``ParquetWriter`` with
         ``OutputStream.tell()`` (#2998).
     """
     from pyiceberg.utils.bin_packing import PackingIterator
 
-    avg_row_size_bytes = tbl.nbytes / tbl.num_rows
+    avg_row_size_bytes = _arrow_data_size(tbl) / tbl.num_rows
     target_rows_per_file = max(1, int(target_file_size / avg_row_size_bytes))
     batches = tbl.to_batches(max_chunksize=target_rows_per_file)
     bin_packed_record_batches = PackingIterator(
         items=batches,
         target_weight=target_file_size,
         lookback=len(batches),  # ignore lookback
-        weight_func=lambda x: x.nbytes,
+        weight_func=_arrow_data_size,
         largest_bin_first=False,
     )
     return bin_packed_record_batches
 
 
+def _arrow_data_size(data: pa.Table | pa.RecordBatch) -> int:
+    """Estimate Arrow data size for writer bin-packing.
+
+    ``nbytes`` is the better logical-size estimate, but PyArrow can raise for
+    view types such as ``string_view`` exported by libraries like Polars. Fall
+    back to total referenced buffer size so those streams can still be written.
+    """
+    try:
+        return data.nbytes
+    except pyarrow.lib.ArrowTypeError:
+        return data.get_total_buffer_size()
+
+
 def bin_pack_record_batches(batches: Iterable[pa.RecordBatch], target_file_size: int) -> Iterator[list[pa.RecordBatch]]:
     """Microbatch a single-pass stream of RecordBatches into target-sized groups.
 
@@ -2719,9 +2734,11 @@ def bin_pack_record_batches(batches: Iterable[pa.RecordBatch], target_file_size:
 
     Note:
         ``target_file_size`` is measured in **uncompressed in-memory** Arrow
-        bytes (``RecordBatch.nbytes``), not compressed on-disk Parquet bytes.
-        The resulting Parquet file after compression is typically 3-10×
-        smaller than ``target_file_size``. Matches the existing
+        bytes, not compressed on-disk Parquet bytes. The size estimate uses
+        ``nbytes`` when available and falls back to referenced buffer size for
+        Arrow view types that do not support ``nbytes``. The resulting Parquet
+        file after compression is typically 3-10× smaller than
+        ``target_file_size``. Matches the existing
         :func:`bin_pack_arrow_table` semantics; both will be tightened to true
         on-disk bytes once the writer is switched to a rolling-
         ``ParquetWriter`` with ``OutputStream.tell()`` (#2998).
@@ -2730,7 +2747,7 @@ def bin_pack_record_batches(batches: Iterable[pa.RecordBatch], target_file_size:
     buffer_bytes = 0
     for batch in batches:
         buffer.append(batch)
-        buffer_bytes += batch.nbytes
+        buffer_bytes += _arrow_data_size(batch)
         if buffer_bytes >= target_file_size:
             yield buffer
             buffer = []
@@ -3033,3 +3050,23 @@ def _get_field_from_arrow_table(arrow_table: pa.Table, field_path: str) -> pa.Ar
     field_array = arrow_table[path_parts[0]]
     # Navigate into the struct using the remaining path parts
     return pc.struct_field(field_array, path_parts[1:])
+
+
+def _coerce_arrow_input(df: pa.Table | pa.RecordBatchReader | ArrowStreamExportable) -> pa.Table | pa.RecordBatchReader:
+    """Normalize Arrow write input to a pa.Table or pa.RecordBatchReader.
+
+    Native pyarrow inputs pass through unchanged; any object implementing the
+    Arrow PyCapsule stream interface (``__arrow_c_stream__``) is imported as a
+    streaming RecordBatchReader.
+    """
+    if isinstance(df, (pa.Table, pa.RecordBatchReader)):
+        return df
+
+    # Any object implementing the Arrow PyCapsule stream interface.
+    if hasattr(df, "__arrow_c_stream__"):
+        return pa.RecordBatchReader.from_stream(df)
+
+    raise ValueError(
+        f"Expected pa.Table, pa.RecordBatchReader, or an object implementing the "
+        f"Arrow PyCapsule interface (__arrow_c_stream__), got: {df!r}"
+    )

pyiceberg/table/__init__.py

@@ -82,6 +82,7 @@
 from pyiceberg.transforms import IdentityTransform
 from pyiceberg.typedef import (
     EMPTY_DICT,
+    ArrowStreamExportable,
     IcebergBaseModel,
     IcebergRootModel,
     Identifier,
@@ -452,7 +453,7 @@ def update_statistics(self) -> UpdateStatistics:
 
     def append(
         self,
-        df: pa.Table | pa.RecordBatchReader,
+        df: pa.Table | pa.RecordBatchReader | ArrowStreamExportable,
         snapshot_properties: dict[str, str] = EMPTY_DICT,
         branch: str | None = MAIN_BRANCH,
     ) -> None:
@@ -505,10 +506,9 @@ def append(
         except ModuleNotFoundError as e:
             raise ModuleNotFoundError("For writes PyArrow needs to be installed") from e
 
-        from pyiceberg.io.pyarrow import _check_pyarrow_schema_compatible, _dataframe_to_data_files
+        from pyiceberg.io.pyarrow import _check_pyarrow_schema_compatible, _coerce_arrow_input, _dataframe_to_data_files
 
-        if not isinstance(df, (pa.Table, pa.RecordBatchReader)):
-            raise ValueError(f"Expected pa.Table or pa.RecordBatchReader, got: {df}")
+        df = _coerce_arrow_input(df)
 
         downcast_ns_timestamp_to_us = Config().get_bool(DOWNCAST_NS_TIMESTAMP_TO_US_ON_WRITE) or False
         _check_pyarrow_schema_compatible(
@@ -598,7 +598,7 @@ def dynamic_partition_overwrite(
 
     def overwrite(
         self,
-        df: pa.Table | pa.RecordBatchReader,
+        df: pa.Table | pa.RecordBatchReader | ArrowStreamExportable,
         overwrite_filter: BooleanExpression | str = ALWAYS_TRUE,
         snapshot_properties: dict[str, str] = EMPTY_DICT,
         case_sensitive: bool = True,
@@ -662,10 +662,9 @@ def overwrite(
         except ModuleNotFoundError as e:
             raise ModuleNotFoundError("For writes PyArrow needs to be installed") from e
 
-        from pyiceberg.io.pyarrow import _check_pyarrow_schema_compatible, _dataframe_to_data_files
+        from pyiceberg.io.pyarrow import _check_pyarrow_schema_compatible, _coerce_arrow_input, _dataframe_to_data_files
 
-        if not isinstance(df, (pa.Table, pa.RecordBatchReader)):
-            raise ValueError(f"Expected pa.Table or pa.RecordBatchReader, got: {df}")
+        df = _coerce_arrow_input(df)
 
         downcast_ns_timestamp_to_us = Config().get_bool(DOWNCAST_NS_TIMESTAMP_TO_US_ON_WRITE) or False
         _check_pyarrow_schema_compatible(
@@ -1472,7 +1471,7 @@ def upsert(
 
     def append(
         self,
-        df: pa.Table | pa.RecordBatchReader,
+        df: pa.Table | pa.RecordBatchReader | ArrowStreamExportable,
         snapshot_properties: dict[str, str] = EMPTY_DICT,
         branch: str | None = MAIN_BRANCH,
     ) -> None:
@@ -1507,7 +1506,7 @@ def dynamic_partition_overwrite(
 
     def overwrite(
         self,
-        df: pa.Table | pa.RecordBatchReader,
+        df: pa.Table | pa.RecordBatchReader | ArrowStreamExportable,
         overwrite_filter: BooleanExpression | str = ALWAYS_TRUE,
         snapshot_properties: dict[str, str] = EMPTY_DICT,
         case_sensitive: bool = True,
@@ -1716,6 +1715,10 @@ def __datafusion_table_provider__(self, session: Any | None = None) -> IcebergDa
         ).__datafusion_table_provider__
         return provider(session)
 
+    def __arrow_c_stream__(self, requested_schema: object | None = None) -> object:
+        """Export this Table as an Arrow C stream (PyCapsule interface)."""
+        return self.scan().to_arrow_batch_reader().__arrow_c_stream__(requested_schema)
+
 
 class StaticTable(Table):
     """Load a table directly from a metadata file (i.e., without using a catalog)."""
@@ -2252,6 +2255,10 @@ def to_arrow_batch_reader(self) -> pa.RecordBatchReader:
             batches,
         ).cast(target_schema)
 
+    def __arrow_c_stream__(self, requested_schema: object | None = None) -> object:
+        """Export this scan's result as an Arrow C stream (PyCapsule interface)."""
+        return self.to_arrow_batch_reader().__arrow_c_stream__(requested_schema)
+
     def to_pandas(self, **kwargs: Any) -> pd.DataFrame:
         """Read a Pandas DataFrame eagerly from this Iceberg table.
 

pyiceberg/typedef.py

@@ -112,6 +112,19 @@ def __setitem__(self, pos: int, value: Any) -> None:
         """Assign a value to a StructProtocol."""
 
 
+@runtime_checkable
+class ArrowStreamExportable(Protocol):  # pragma: no cover
+    """Any object implementing the Arrow PyCapsule stream interface.
+
+    Covers pa.Table, pa.RecordBatchReader, and third-party producers
+    (polars, arro3, nanoarrow, ...) without depending on any of them.
+    """
+
+    @abstractmethod
+    def __arrow_c_stream__(self, requested_schema: object | None = None) -> object:
+        """Export the object as an Arrow C stream PyCapsule."""
+
+
 class IcebergBaseModel(BaseModel):
     """
     This class extends the Pydantic BaseModel to set default values by overriding them.

tests/catalog/test_catalog_behaviors.py

@@ -1318,7 +1318,7 @@ def test_append_invalid_input_type_raises(catalog: Catalog) -> None:
     identifier = f"default.append_invalid_input_{catalog.name}"
     pa_table = _simple_arrow_table()
     tbl = catalog.create_table(identifier=identifier, schema=pa_table.schema)
-    with pytest.raises(ValueError, match="Expected pa.Table or pa.RecordBatchReader"):
+    with pytest.raises(ValueError, match="Expected pa.Table, pa.RecordBatchReader, or an object implementing"):
         tbl.append("not an arrow object")
 
 

tests/integration/test_writes/test_partitioned_writes.py

@@ -768,7 +768,7 @@ def test_invalid_arguments(spark: SparkSession, session_catalog: Catalog) -> Non
         properties={"format-version": "1"},
     )
 
-    with pytest.raises(ValueError, match="Expected pa.Table or pa.RecordBatchReader, got: not a df"):
+    with pytest.raises(ValueError, match="Expected pa.Table, pa.RecordBatchReader, or an object implementing"):
         tbl.append("not a df")
 
 

tests/integration/test_writes/test_writes.py

@@ -791,10 +791,10 @@ def test_invalid_arguments(spark: SparkSession, session_catalog: Catalog, arrow_
     identifier = "default.arrow_data_files"
     tbl = _create_table(session_catalog, identifier, {"format-version": "1"}, [])
 
-    with pytest.raises(ValueError, match="Expected pa.Table or pa.RecordBatchReader, got: not a df"):
+    with pytest.raises(ValueError, match="Expected pa.Table, pa.RecordBatchReader, or an object implementing"):
         tbl.overwrite("not a df")
 
-    with pytest.raises(ValueError, match="Expected pa.Table or pa.RecordBatchReader, got: not a df"):
+    with pytest.raises(ValueError, match="Expected pa.Table, pa.RecordBatchReader, or an object implementing"):
         tbl.append("not a df")
 
 

tests/io/test_pyarrow.py

@@ -2435,6 +2435,17 @@ def test_bin_pack_arrow_table_target_size_smaller_than_row(arrow_table_with_null
     assert sum(batch.num_rows for bin_ in bin_packed for batch in bin_) == arrow_table_with_null.num_rows
 
 
+def test_bin_pack_arrow_table_with_string_view() -> None:
+    if not hasattr(pa, "string_view"):
+        pytest.skip("pyarrow does not support string_view")
+
+    table = pa.table({"region": pa.array(["ca", "mx"], type=pa.string_view())})
+
+    bins = list(bin_pack_arrow_table(table, target_file_size=1))
+
+    assert sum(batch.num_rows for bin_ in bins for batch in bin_) == table.num_rows
+
+
 def test_bin_pack_record_batches_single_bin(arrow_table_with_null: pa.Table) -> None:
     batches = arrow_table_with_null.to_batches()
     bins = list(bin_pack_record_batches(iter(batches), target_file_size=arrow_table_with_null.nbytes * 10))