Skip to content

Add support for using ListView arrays and types through FFI #8822

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
alamb merged 7 commits into from
Dec 4, 2025
Merged

Add support for using ListView arrays and types through FFI #8822

Show file tree
Hide file tree
Changes from 4 commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
d0980b1
Schema support
AdamGS Nov 11, 2025
ff3dc75
Add support for arrays
AdamGS Nov 11, 2025
7375a94
Add pyarrow integration test
AdamGS Nov 11, 2025
c0e5df9
Fix python tests
AdamGS Nov 11, 2025
cedca3b
Merge branch 'main' into adamg/ffi-list-view
AdamGS Nov 21, 2025
6c0e7a4
Merge branch 'main' into adamg/ffi-list-view
alamb Dec 3, 2025
5b00813
Fix ArrayData::new_null post merge
AdamGS Dec 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
146 changes: 143 additions & 3 deletions arrow-array/src/ffi.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -140,8 +140,8 @@ pub unsafe fn export_array_into_raw(
Ok(())
}

// returns the number of bits that buffer `i` (in the C data interface) is expected to have.
// This is set by the Arrow specification
/// returns the number of bits that buffer `i` (in the C data interface) is expected to have.
Copy link
Copy Markdown
Contributor Author

@AdamGS AdamGS Nov 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Just nicer when working with IDEs.

/// This is set by the Arrow specification
fn bit_width(data_type: &DataType, i: usize) -> Result<usize> {
if let Some(primitive) = data_type.primitive_width() {
return match i {
Expand Down Expand Up @@ -180,6 +180,10 @@ fn bit_width(data_type: &DataType, i: usize) -> Result<usize> {
| (DataType::List(_), 1)
| (DataType::Map(_, _), 1) => i32::BITS as _,
(DataType::Utf8, 2) | (DataType::Binary, 2) => u8::BITS as _,
// List views have two i32 buffers, offsets and sizes
(DataType::ListView(_), 1) | (DataType::ListView(_), 2) => i32::BITS as _,
// Large list views have two i64 buffers, offsets and sizes
(DataType::LargeListView(_), 1) | (DataType::LargeListView(_), 2) => i64::BITS as _,
(DataType::List(_), _) | (DataType::Map(_, _), _) => {
return Err(ArrowError::CDataInterface(format!(
"The datatype \"{data_type}\" expects 2 buffers, but requested {i}. Please verify that the C data interface is correctly implemented."
Expand Down Expand Up @@ -351,6 +355,8 @@ impl ImportedArrowArray<'_> {
DataType::List(field)
| DataType::FixedSizeList(field, _)
| DataType::LargeList(field)
| DataType::ListView(field)
| DataType::LargeListView(field)
| DataType::Map(field, _) => Ok([self.consume_child(0, field.data_type())?].to_vec()),
DataType::Struct(fields) => {
assert!(fields.len() == self.array.num_children());
Expand Down Expand Up @@ -471,6 +477,14 @@ impl ImportedArrowArray<'_> {
debug_assert_eq!(bits % 8, 0);
(length + 1) * (bits / 8)
}
(DataType::ListView(_), 1)
| (DataType::ListView(_), 2)
| (DataType::LargeListView(_), 1)
| (DataType::LargeListView(_), 2) => {
let bits = bit_width(data_type, i)?;
debug_assert_eq!(bits % 8, 0);
length * (bits / 8)
}
(DataType::Utf8, 2) | (DataType::Binary, 2) => {
if self.array.is_empty() {
return Ok(0);
Expand Down Expand Up @@ -553,7 +567,7 @@ mod tests_to_then_from_ffi {
use std::collections::HashMap;
use std::mem::ManuallyDrop;

use arrow_buffer::NullBuffer;
use arrow_buffer::{ArrowNativeType, NullBuffer};
use arrow_schema::Field;

use crate::builder::UnionBuilder;
Expand Down Expand Up @@ -783,6 +797,71 @@ mod tests_to_then_from_ffi {
test_generic_list::<i64>()
}

fn test_generic_list_view<Offset: OffsetSizeTrait + ArrowNativeType>() -> Result<()> {
// Construct a value array
let value_data = ArrayData::builder(DataType::Int16)
.len(8)
.add_buffer(Buffer::from_slice_ref([0_i16, 1, 2, 3, 4, 5, 6, 7]))
.build()
.unwrap();

// Construct a buffer for value offsets, for the nested array:
// [[0, 1, 2], [3, 4, 5], [6, 7]]
let value_offsets = [0_usize, 3, 6]
.iter()
.map(|i| Offset::from_usize(*i).unwrap())
.collect::<Buffer>();

let sizes_buffer = [3_usize, 3, 2]
.iter()
.map(|i| Offset::from_usize(*i).unwrap())
.collect::<Buffer>();

// Construct a list array from the above two
let list_view_dt = GenericListViewArray::<Offset>::DATA_TYPE_CONSTRUCTOR(Arc::new(
Field::new_list_field(DataType::Int16, false),
));

let list_data = ArrayData::builder(list_view_dt)
.len(3)
.add_buffer(value_offsets)
.add_buffer(sizes_buffer)
.add_child_data(value_data)
.build()
.unwrap();

let original = GenericListViewArray::<Offset>::from(list_data.clone());

// export it
let (array, schema) = to_ffi(&original.to_data())?;

// (simulate consumer) import it
let data = unsafe { from_ffi(array, &schema) }?;
let array = make_array(data);

// downcast
let array = array
.as_any()
.downcast_ref::<GenericListViewArray<Offset>>()
.unwrap();

assert_eq!(&array.value(0), &original.value(0));
assert_eq!(&array.value(1), &original.value(1));
assert_eq!(&array.value(2), &original.value(2));

Ok(())
}

#[test]
fn test_list_view() -> Result<()> {
test_generic_list_view::<i32>()
}

#[test]
fn test_large_list_view() -> Result<()> {
test_generic_list_view::<i64>()
}

fn test_generic_binary<Offset: OffsetSizeTrait>() -> Result<()> {
// create an array natively
let array: Vec<Option<&[u8]>> = vec![Some(b"a"), None, Some(b"aaa")];
Expand Down Expand Up @@ -1315,6 +1394,7 @@ mod tests_from_ffi {
use std::ptr::NonNull;
use std::sync::Arc;

use arrow_buffer::NullBuffer;
#[cfg(not(feature = "force_validate"))]
use arrow_buffer::{ScalarBuffer, bit_util, buffer::Buffer};
#[cfg(feature = "force_validate")]
Expand All @@ -1325,6 +1405,7 @@ mod tests_from_ffi {
use arrow_schema::{DataType, Field};

use super::Result;

use crate::builder::GenericByteViewBuilder;
use crate::types::{BinaryViewType, ByteViewType, Int32Type, StringViewType};
use crate::{
Expand Down Expand Up @@ -1528,6 +1609,65 @@ mod tests_from_ffi {
test_round_trip(&data)
}

#[test]
fn test_list_view() -> Result<()> {
// Construct a value array
let value_data = ArrayData::builder(DataType::Int16)
.len(8)
.add_buffer(Buffer::from_slice_ref([0_i16, 1, 2, 3, 4, 5, 6, 7]))
.build()
.unwrap();

// Construct a buffer for value offsets, for the nested array:
// [[0, 1, 2], [3, 4, 5], [6, 7]]
let value_offsets = Buffer::from(vec![0_i32, 3, 6]);
let sizes_buffer = Buffer::from(vec![3_i32, 3, 2]);

// Construct a list array from the above two
let list_view_dt =
DataType::ListView(Arc::new(Field::new_list_field(DataType::Int16, false)));

let list_view_data = ArrayData::builder(list_view_dt)
.len(3)
.add_buffer(value_offsets)
.add_buffer(sizes_buffer)
.add_child_data(value_data)
.build()
.unwrap();

test_round_trip(&list_view_data)
}

#[test]
fn test_list_view_with_nulls() -> Result<()> {
// Construct a value array
let value_data = ArrayData::builder(DataType::Int16)
.len(8)
.add_buffer(Buffer::from_slice_ref([0_i16, 1, 2, 3, 4, 5, 6, 7]))
.build()
.unwrap();

// Construct a buffer for value offsets, for the nested array:
// [[0, 1, 2], [3, 4, 5], [6, 7], null]
let value_offsets = Buffer::from(vec![0_i32, 3, 6, 8]);
let sizes_buffer = Buffer::from(vec![3_i32, 3, 2, 0]);

// Construct a list array from the above two
let list_view_dt =
DataType::ListView(Arc::new(Field::new_list_field(DataType::Int16, true)));

let list_view_data = ArrayData::builder(list_view_dt)
.len(4)
.add_buffer(value_offsets)
.add_buffer(sizes_buffer)
.add_child_data(value_data)
.nulls(Some(NullBuffer::from(vec![true, true, true, false])))
.build()
.unwrap();

test_round_trip(&list_view_data)
}

#[test]
#[cfg(not(feature = "force_validate"))]
fn test_empty_string_with_non_zero_offset() -> Result<()> {
Expand Down
12 changes: 11 additions & 1 deletion arrow-data/src/data.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -620,6 +620,16 @@ impl ArrayData {
vec![ArrayData::new_null(f.data_type(), *list_len as usize * len)],
true,
),
DataType::ListView(f) => (
vec![zeroed(len * 4), zeroed(len * 4)],
vec![ArrayData::new_empty(f.data_type())],
true,
),
DataType::LargeListView(f) => (
vec![zeroed(len * 8), zeroed(len * 8)],
vec![ArrayData::new_empty(f.data_type())],
true,
),
DataType::Struct(fields) => (
vec![],
fields
Expand Down Expand Up @@ -1783,7 +1793,7 @@ impl DataTypeLayout {
},
],
can_contain_null_mask: true,
variadic: true,
variadic: false,
Copy link
Copy Markdown
Contributor Author

@AdamGS AdamGS Nov 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is a bug, see the spec, list views aren't represented by a variable number of buffers.

}
}
}
Expand Down
37 changes: 28 additions & 9 deletions arrow-pyarrow-integration-testing/tests/test_sql.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,9 @@

import arrow_pyarrow_integration_testing as rust

PYARROW_PRE_14 = int(pa.__version__.split('.')[0]) < 14
PYARROW_MAJOR_VER = int(pa.__version__.split(".")[0])
PYARROW_PRE_14 = PYARROW_MAJOR_VER < 14
PYARROW_PRE_16 = PYARROW_MAJOR_VER < 16


@contextlib.contextmanager
Expand Down Expand Up @@ -112,8 +114,16 @@ def assert_pyarrow_leak():
),
]

_unsupported_pyarrow_types = [
]
if PYARROW_MAJOR_VER >= 16:
Copy link
Copy Markdown
Contributor Author

@AdamGS AdamGS Nov 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Did this to get everything green, but I think that it might be a good opportunity to only test with pyarrow 16 and above, which supports all relevant features here - stringview, bianryview and listview and the pycapsule API.
By the time this change (if accepted) will be released, pyarrow 15 will be almost two years old, which seems like enough time to drop dedicated testing for it. This will allow the CI to focus on more relevant releases that also include all the APIs arrow-rs supports.

Copy link
Copy Markdown
Contributor

@alamb alamb Dec 3, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you file a follow on ticket / PR to discuss dropping support for versions less than 16?

Copy link
Copy Markdown
Contributor Author

@AdamGS AdamGS Dec 3, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

will do

Copy link
Copy Markdown
Contributor Author

@AdamGS AdamGS Dec 3, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

#8949

_supported_pyarrow_types.extend(
[
pa.list_view(pa.uint64()),
pa.large_list_view(pa.uint64()),
pa.list_view(pa.string()),
pa.large_list_view(pa.string()),
]
)


# As of pyarrow 14, pyarrow implements the Arrow PyCapsule interface
# (https://arrow.apache.org/docs/format/CDataInterface/PyCapsuleInterface.html).
Expand Down Expand Up @@ -158,12 +168,6 @@ def test_type_roundtrip_pycapsule(pyarrow_type):
assert restored == pyarrow_type
assert restored is not pyarrow_type


@pytest.mark.parametrize("pyarrow_type", _unsupported_pyarrow_types, ids=str)
def test_type_roundtrip_raises(pyarrow_type):
with pytest.raises(pa.ArrowException):
rust.round_trip_type(pyarrow_type)

@pytest.mark.parametrize('pyarrow_type', _supported_pyarrow_types, ids=str)
def test_field_roundtrip(pyarrow_type):
pyarrow_field = pa.field("test", pyarrow_type, nullable=True)
Expand Down Expand Up @@ -337,6 +341,21 @@ def test_list_array():
del a
del b


@pytest.mark.skipif(PYARROW_PRE_16, reason="requires pyarrow 16")
def test_list_view_array():
"""
Python -> Rust -> Python
"""
a = pa.array([[], None, [1, 2], [4, 5, 6]], pa.list_view(pa.int64()))
b = rust.round_trip_array(a)
b.validate(full=True)
assert a.to_pylist() == b.to_pylist()
assert a.type == b.type
del a
del b


def test_map_array():
"""
Python -> Rust -> Python
Expand Down
22 changes: 22 additions & 0 deletions arrow-schema/src/ffi.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -456,6 +456,14 @@ impl TryFrom<&FFI_ArrowSchema> for DataType {
let c_child = c_schema.child(0);
DataType::LargeList(Arc::new(Field::try_from(c_child)?))
}
"+vl" => {
Copy link
Copy Markdown
Contributor

@alamb alamb Dec 3, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Double checked that this matches https://arrow.apache.org/docs/format/CDataInterface.html#data-type-description-format-strings ✅

let c_child = c_schema.child(0);
DataType::ListView(Arc::new(Field::try_from(c_child)?))
}
"+vL" => {
let c_child = c_schema.child(0);
DataType::LargeListView(Arc::new(Field::try_from(c_child)?))
}
"+s" => {
let fields = c_schema.children().map(Field::try_from);
DataType::Struct(fields.collect::<Result<_, ArrowError>>()?)
Expand Down Expand Up @@ -657,6 +665,8 @@ impl TryFrom<&DataType> for FFI_ArrowSchema {
let children = match dtype {
DataType::List(child)
| DataType::LargeList(child)
| DataType::ListView(child)
| DataType::LargeListView(child)
| DataType::FixedSizeList(child, _)
| DataType::Map(child, _) => {
vec![FFI_ArrowSchema::try_from(child.as_ref())?]
Expand Down Expand Up @@ -746,6 +756,8 @@ fn get_format_string(dtype: &DataType) -> Result<Cow<'static, str>, ArrowError>
DataType::Interval(IntervalUnit::MonthDayNano) => Ok("tin".into()),
DataType::List(_) => Ok("+l".into()),
DataType::LargeList(_) => Ok("+L".into()),
DataType::ListView(_) => Ok("+vl".into()),
DataType::LargeListView(_) => Ok("+vL".into()),
DataType::Struct(_) => Ok("+s".into()),
DataType::Map(_, _) => Ok("+m".into()),
DataType::RunEndEncoded(_, _) => Ok("+r".into()),
Expand Down Expand Up @@ -874,6 +886,16 @@ mod tests {
DataType::Int16,
false,
))));
round_trip_type(DataType::ListView(Arc::new(Field::new(
"a",
DataType::Int16,
false,
))));
round_trip_type(DataType::LargeListView(Arc::new(Field::new(
"a",
DataType::Int16,
false,
))));
round_trip_type(DataType::Struct(Fields::from(vec![Field::new(
"a",
DataType::Utf8,
Expand Down
Loading