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Avoid a clone when creating ListViewArray from ArrayData #9193

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Merged
alamb merged 5 commits into from
Jan 18, 2026
Merged

Avoid a clone when creating ListViewArray from ArrayData #9193

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72d0fcc
Avoid a clone when creating `ListViewArray` from ArrayData
alamb Jan 15, 2026
1ce74ff
Merge branch 'main' into alamb/list_view_array
alamb Jan 16, 2026
3f63baf
listview
alamb Jan 17, 2026
b910463
Revert "Avoid a clone when creating `ListArray` from ArrayData"
alamb Jan 17, 2026
d28a730
Simplify
alamb Jan 17, 2026
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43 changes: 22 additions & 21 deletions arrow-array/src/array/list_view_array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
// specific language governing permissions and limitations
// under the License.

use arrow_buffer::{NullBuffer, ScalarBuffer};
use arrow_buffer::{Buffer, NullBuffer, ScalarBuffer};
use arrow_data::{ArrayData, ArrayDataBuilder};
use arrow_schema::{ArrowError, DataType, FieldRef};
use std::any::Any;
Expand Down Expand Up @@ -576,23 +576,25 @@ impl<OffsetSize: OffsetSizeTrait> From<FixedSizeListArray> for GenericListViewAr

impl<OffsetSize: OffsetSizeTrait> GenericListViewArray<OffsetSize> {
fn try_new_from_array_data(data: ArrayData) -> Result<Self, ArrowError> {
if data.buffers().len() != 2 {
return Err(ArrowError::InvalidArgumentError(format!(
"ListViewArray data should contain two buffers (value offsets & value sizes), had {}",
data.buffers().len()
)));
}
let (data_type, len, nulls, offset, buffers, child_data) = data.into_parts();

if data.child_data().len() != 1 {
return Err(ArrowError::InvalidArgumentError(format!(
"ListViewArray should contain a single child array (values array), had {}",
data.child_data().len()
)));
}
// ArrayData is valid, and verified type above
// buffer[0] is offsets, buffer[1] is sizes
let num_buffers = buffers.len();
let [offsets_buffer, sizes_buffer] : [Buffer; 2] = buffers.try_into().map_err(|_| {
ArrowError::InvalidArgumentError(format!(
"ListViewArray data should contain two buffers (value offsets & value sizes), had {num_buffers}",
))
})?;

let values = data.child_data()[0].clone();
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@alamb alamb Jan 17, 2026

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This saves a real clone of ArrayData (and thus an allocation)

let num_child = child_data.len();
let [values]: [ArrayData; 1] = child_data.try_into().map_err(|_| {
ArrowError::InvalidArgumentError(format!(
"ListViewArray should contain a single child array (values array), had {num_child}",
))
})?;

if let Some(child_data_type) = Self::get_type(data.data_type()) {
if let Some(child_data_type) = Self::get_type(&data_type) {
if values.data_type() != child_data_type {
return Err(ArrowError::InvalidArgumentError(format!(
"{}ListViewArray's child datatype {:?} does not \
Expand All @@ -607,18 +609,17 @@ impl<OffsetSize: OffsetSizeTrait> GenericListViewArray<OffsetSize> {
"{}ListViewArray's datatype must be {}ListViewArray(). It is {:?}",
OffsetSize::PREFIX,
OffsetSize::PREFIX,
data.data_type()
data_type
)));
}

let values = make_array(values);
// ArrayData is valid, and verified type above
let value_offsets = ScalarBuffer::new(data.buffers()[0].clone(), data.offset(), data.len());
let value_sizes = ScalarBuffer::new(data.buffers()[1].clone(), data.offset(), data.len());
let value_offsets = ScalarBuffer::new(offsets_buffer, offset, len);
let value_sizes = ScalarBuffer::new(sizes_buffer, offset, len);

Ok(Self {
data_type: data.data_type().clone(),
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@alamb alamb Jan 17, 2026

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This saves a DataType::drop and a clone of NullBuffer -- probably not a huge deal but unecessary

nulls: data.nulls().cloned(),
data_type,
nulls,
values,
value_offsets,
value_sizes,
Expand Down
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