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Avoid a clone when creating ListArray from ArrayData #9194

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Merged
alamb merged 2 commits into from
Jan 18, 2026
Merged

Avoid a clone when creating ListArray from ArrayData #9194

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c7a524a
Avoid a clone when creating `ListArray` from ArrayData
alamb Jan 15, 2026
e7ba892
Merge branch 'main' into alamb/avoid_list_array
alamb Jan 16, 2026
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26 changes: 14 additions & 12 deletions arrow-array/src/array/list_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 crate::array::{get_offsets, make_array, print_long_array};
use crate::array::{get_offsets_from_buffer, make_array, print_long_array};
use crate::builder::{GenericListBuilder, PrimitiveBuilder};
use crate::{
Array, ArrayAccessor, ArrayRef, ArrowPrimitiveType, FixedSizeListArray,
Expand Down Expand Up @@ -479,23 +479,26 @@ impl<OffsetSize: OffsetSizeTrait> From<FixedSizeListArray> for GenericListArray<

impl<OffsetSize: OffsetSizeTrait> GenericListArray<OffsetSize> {
fn try_new_from_array_data(data: ArrayData) -> Result<Self, ArrowError> {
if data.buffers().len() != 1 {
let (data_type, len, nulls, offset, mut buffers, mut child_data) = data.into_parts();

if buffers.len() != 1 {
return Err(ArrowError::InvalidArgumentError(format!(
"ListArray data should contain a single buffer only (value offsets), had {}",
data.buffers().len()
buffers.len()
)));
}
let buffer = buffers.pop().expect("checked above");

if data.child_data().len() != 1 {
if child_data.len() != 1 {
return Err(ArrowError::InvalidArgumentError(format!(
"ListArray should contain a single child array (values array), had {}",
data.child_data().len()
child_data.len()
)));
}

let values = data.child_data()[0].clone();
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@alamb alamb Jan 15, 2026 •
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here we save a clone of ArrayData (and thus a Vec allocation)

let values = child_data.pop().expect("checked above");

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!(
"[Large]ListArray's child datatype {:?} does not \
Expand All @@ -506,19 +509,18 @@ impl<OffsetSize: OffsetSizeTrait> GenericListArray<OffsetSize> {
}
} else {
return Err(ArrowError::InvalidArgumentError(format!(
"[Large]ListArray's datatype must be [Large]ListArray(). It is {:?}",
data.data_type()
"[Large]ListArray's datatype must be [Large]ListArray(). It is {data_type:?}",
)));
}

let values = make_array(values);
// SAFETY:
// ArrayData is valid, and verified type above
let value_offsets = unsafe { get_offsets(&data) };
let value_offsets = unsafe { get_offsets_from_buffer(buffer, offset, len) };

Ok(Self {
data_type: data.data_type().clone(),
nulls: data.nulls().cloned(),
data_type,
nulls,
values,
value_offsets,
})
Expand Down
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