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Avoid clones in make_array for StructArray and GenericByteViewArray #9114

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Merged
alamb merged 4 commits into from
Jan 12, 2026
+46 −14
Merged

Avoid clones in make_array for StructArray and GenericByteViewArray #9114

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372b59c
Avoid clones in `make_array` for `StructArray` and `GenericByteViewAr…
alamb Jan 7, 2026
4895eda
Merge remote-tracking branch 'apache/main' into alamb/struct_array_cl…
alamb Jan 10, 2026
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alamb Jan 11, 2026
59d9035
Merge remote-tracking branch 'apache/main' into alamb/struct_array_cl…
alamb Jan 11, 2026
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11 changes: 6 additions & 5 deletions arrow-array/src/array/byte_view_array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -967,15 +967,16 @@ impl<'a, T: ByteViewType + ?Sized> IntoIterator for &'a GenericByteViewArray<T>
}

impl<T: ByteViewType + ?Sized> From<ArrayData> for GenericByteViewArray<T> {
fn from(value: ArrayData) -> Self {
let views = value.buffers()[0].clone();
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@alamb alamb Jan 7, 2026 •
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cloneing the buffers is relatively cheap (they are Arcd internally) so avoiding this just makes the code easier to follow, I don't think it will be any significant performance savings

let views = ScalarBuffer::new(views, value.offset(), value.len());
let buffers = value.buffers()[1..].to_vec().into();
fn from(data: ArrayData) -> Self {
let (_data_type, len, nulls, offset, mut buffers, _child_data) = data.into_parts();
let views = buffers.remove(0); // need to maintain order of remaining buffers
let buffers = Arc::from(buffers);
let views = ScalarBuffer::new(views, offset, len);
Self {
data_type: T::DATA_TYPE,
views,
buffers,
nulls: value.nulls().cloned(),
nulls,
phantom: Default::default(),
}
}
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19 changes: 10 additions & 9 deletions arrow-array/src/array/struct_array.rs
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Expand Up @@ -347,25 +347,26 @@ impl StructArray {

impl From<ArrayData> for StructArray {
fn from(data: ArrayData) -> Self {
let parent_offset = data.offset();
let parent_len = data.len();
let (data_type, len, nulls, offset, _buffers, child_data) = data.into_parts();

let fields = data
.child_data()
.iter()
let parent_offset = offset;
let parent_len = len;

let fields = child_data
.into_iter()
.map(|cd| {
if parent_offset != 0 || parent_len != cd.len() {
make_array(cd.slice(parent_offset, parent_len))
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@alamb alamb Jan 7, 2026

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we can probably avoid an additional allocation for sliced arrays by making a version of slice() that consumes self -- like sliced() perhaps 🤔

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@alamb alamb Jan 11, 2026

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I filed a ticket to track this idea

} else {
make_array(cd.clone())
make_array(cd)
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@alamb alamb Jan 7, 2026

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cd.clone() clones the ArrayData (and allocates a new Vec) for each child, recursively, which is unecessary

}
})
.collect();

Self {
len: data.len(),
data_type: data.data_type().clone(),
nulls: data.nulls().cloned(),
len,
data_type,
nulls,
fields,
}
}
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30 changes: 30 additions & 0 deletions arrow-data/src/data.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -309,6 +309,9 @@ impl ArrayData {
///
/// Note: This is a low level API and most users of the arrow crate should create
/// arrays using the builders found in [arrow_array](https://docs.rs/arrow-array)
/// or [`ArrayDataBuilder`].
///
/// See also [`Self::into_parts`] to recover the fields
pub fn try_new(
data_type: DataType,
len: usize,
Expand Down Expand Up @@ -351,6 +354,33 @@ impl ArrayData {
Ok(new_self)
}

/// Return the constituent parts of this ArrayData
///
/// This is the inverse of [`ArrayData::try_new`].
///
/// Returns `(data_type, len, nulls, offset, buffers, child_data)`
pub fn into_parts(
self,
) -> (
DataType,
usize,
Option<NullBuffer>,
usize,
Vec<Buffer>,
Vec<ArrayData>,
) {
let Self {
data_type,
len,
nulls,
offset,
buffers,
child_data,
} = self;

(data_type, len, nulls, offset, buffers, child_data)
}

/// Returns a builder to construct a [`ArrayData`] instance of the same [`DataType`]
#[inline]
pub const fn builder(data_type: DataType) -> ArrayDataBuilder {
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