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Avoid a clone when creating FixedSizeListArray from ArrayData #9187

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Merged
alamb merged 3 commits into from
Jan 21, 2026
Merged

Avoid a clone when creating FixedSizeListArray from ArrayData #9187

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c57d26c
Avoid a clone when creating `FixedSizeListArray` from ArrayData
alamb Jan 15, 2026
a66fb5b
Merge branch 'main' into alamb/fixed_slize_list
alamb Jan 18, 2026
7e7bc6e
Merge branch 'main' into alamb/fixed_slize_list
alamb Jan 18, 2026
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15 changes: 8 additions & 7 deletions arrow-array/src/array/fixed_size_list_array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -429,8 +429,10 @@ impl FixedSizeListArray {

impl From<ArrayData> for FixedSizeListArray {
fn from(data: ArrayData) -> Self {
let value_length = match data.data_type() {
DataType::FixedSizeList(_, len) => *len,
let (data_type, len, nulls, offset, _buffers, child_data) = data.into_parts();

let value_length = match data_type {
DataType::FixedSizeList(_, len) => len,
data_type => {
panic!(
"FixedSizeListArray data should contain a FixedSizeList data type, got {data_type}"
Expand All @@ -439,14 +441,13 @@ impl From<ArrayData> for FixedSizeListArray {
};

let size = value_length as usize;
let values =
make_array(data.child_data()[0].slice(data.offset() * size, data.len() * size));
let values = make_array(child_data[0].slice(offset * size, len * size));
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@alamb alamb Jan 15, 2026

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this still bothers me -- slice() allocates a bunch of new children ArrayDatas when I think it could mutate them in place. I'll see what I can do as a follow on PR

Self {
data_type: data.data_type().clone(),
data_type,
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@alamb alamb Jan 18, 2026

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this avoids a DataType::drop and a clone of a NullBuffer -- I don't expect this to be a huge deal performance wise but I am trying to make all the From impls consistent

values,
nulls: data.nulls().cloned(),
nulls,
value_length,
len: data.len(),
len,
}
}
}
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