Skip to content

Avoid a clone when creating UnionArray from ArrayData #9188

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
Dandandan merged 2 commits into from
Jan 18, 2026
Merged

Avoid a clone when creating UnionArray from ArrayData #9188

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ff4a428
Avoid a clone when creating `UnionArray` from ArrayData
alamb Jan 15, 2026
3717507
Merge branch 'main' into alamb/union_array
alamb Jan 16, 2026
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
40 changes: 22 additions & 18 deletions arrow-array/src/array/union_array.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@
use crate::{Array, ArrayRef, make_array};
use arrow_buffer::bit_chunk_iterator::{BitChunkIterator, BitChunks};
use arrow_buffer::buffer::NullBuffer;
use arrow_buffer::{BooleanBuffer, MutableBuffer, ScalarBuffer};
use arrow_buffer::{BooleanBuffer, Buffer, MutableBuffer, ScalarBuffer};
use arrow_data::{ArrayData, ArrayDataBuilder};
use arrow_schema::{ArrowError, DataType, UnionFields, UnionMode};
/// Contains the `UnionArray` type.
Expand Down Expand Up @@ -680,32 +680,36 @@ impl UnionArray {

impl From<ArrayData> for UnionArray {
fn from(data: ArrayData) -> Self {
let (fields, mode) = match data.data_type() {
DataType::Union(fields, mode) => (fields, *mode),
let (data_type, len, _nulls, offset, buffers, child_data) = data.into_parts();

let (fields, mode) = match &data_type {
DataType::Union(fields, mode) => (fields, mode),
d => panic!("UnionArray expected ArrayData with type Union got {d}"),
};

let (type_ids, offsets) = match mode {
UnionMode::Sparse => (
ScalarBuffer::new(data.buffers()[0].clone(), data.offset(), data.len()),
None,
),
UnionMode::Dense => (
ScalarBuffer::new(data.buffers()[0].clone(), data.offset(), data.len()),
Some(ScalarBuffer::new(
data.buffers()[1].clone(),
data.offset(),
data.len(),
)),
),
UnionMode::Sparse => {
let [buffer]: [Buffer; 1] = buffers.try_into().expect("1 buffer for type_ids");
(ScalarBuffer::new(buffer, offset, len), None)
}
UnionMode::Dense => {
let [type_ids_buffer, offsets_buffer]: [Buffer; 2] = buffers
.try_into()
.expect("2 buffers for type_ids and offsets");
(
ScalarBuffer::new(type_ids_buffer, offset, len),
Some(ScalarBuffer::new(offsets_buffer, offset, len)),
)
}
};

let max_id = fields.iter().map(|(i, _)| i).max().unwrap_or_default() as usize;
let mut boxed_fields = vec![None; max_id + 1];
for (cd, (field_id, _)) in data.child_data().iter().zip(fields.iter()) {
boxed_fields[field_id as usize] = Some(make_array(cd.clone()));
for (cd, (field_id, _)) in child_data.into_iter().zip(fields.iter()) {
boxed_fields[field_id as usize] = Some(make_array(cd));
Copy link
Contributor Author

@alamb alamb Jan 15, 2026 •
edited
Loading

Choose a reason for hiding this comment

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

this saves a clone of ArrayData (which each requires a Vec allocation) for each child of the UnionArray

}
Self {
data_type: data.data_type().clone(),
data_type,
Copy link
Contributor Author

@alamb alamb Jan 16, 2026

Choose a reason for hiding this comment

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

this saves a call of DataType::drop

type_ids,
offsets,
fields: boxed_fields,
Expand Down
Loading