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Make array_reverse faster for List and FixedSizeList #18500

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7f3dc5c
Improve performance of array_reverse 5x by using take, not MutableData
vegarsti Nov 5, 2025
38af34a
Add a test for reversing a FixedSizeList with nulls
vegarsti Nov 5, 2025
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53 changes: 32 additions & 21 deletions datafusion/functions-nested/src/reverse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,8 @@

use crate::utils::make_scalar_function;
use arrow::array::{
Array, ArrayRef, Capacities, FixedSizeListArray, GenericListArray,
GenericListViewArray, MutableArrayData, OffsetSizeTrait, UInt32Array,
Array, ArrayRef, FixedSizeListArray, GenericListArray, GenericListViewArray,
OffsetSizeTrait, UInt32Array, UInt64Array,
};
use arrow::buffer::{OffsetBuffer, ScalarBuffer};
use arrow::compute::take;
Expand Down Expand Up @@ -155,11 +155,8 @@ fn general_array_reverse<O: OffsetSizeTrait>(
field: &FieldRef,
) -> Result<ArrayRef> {
let values = array.values();
let original_data = values.to_data();
let capacity = Capacities::Array(original_data.len());
let mut offsets = vec![O::usize_as(0)];
let mut mutable =
MutableArrayData::with_capacities(vec![&original_data], false, capacity);
let mut indices: Vec<O> = Vec::with_capacity(values.len());

for (row_index, (&start, &end)) in array.offsets().iter().tuple_windows().enumerate()
{
Expand All @@ -171,18 +168,34 @@ fn general_array_reverse<O: OffsetSizeTrait>(

let mut index = end - O::one();
while index >= start {
mutable.extend(0, index.to_usize().unwrap(), index.to_usize().unwrap() + 1);
indices.push(index);
index = index - O::one();
}
let size = end - start;
offsets.push(offsets[row_index] + size);
}

let data = mutable.freeze();
// Materialize values from underlying array with take
let indices_array: ArrayRef = if O::IS_LARGE {
Arc::new(UInt64Array::from(
indices
.iter()
.map(|i| i.as_usize() as u64)
.collect::<Vec<_>>(),
))
} else {
Arc::new(UInt32Array::from(
indices
.iter()
.map(|i| i.as_usize() as u32)
.collect::<Vec<_>>(),
))
};
Comment on lines +178 to +193
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@vegarsti vegarsti Nov 5, 2025

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This is duplicated for ListView. I figured twice was not enough to extract to a function, but if we find a nicer way to do it, we can improve both.

let values = take(&values, &indices_array, None)?;
Ok(Arc::new(GenericListArray::<O>::try_new(
Arc::clone(field),
OffsetBuffer::<O>::new(offsets.into()),
arrow::array::make_array(data),
values,
array.nulls().cloned(),
)?))
}
Expand Down Expand Up @@ -231,7 +244,7 @@ fn list_view_reverse<O: OffsetSizeTrait>(

// Materialize values from underlying array with take
let indices_array: ArrayRef = if O::IS_LARGE {
Arc::new(arrow::array::UInt64Array::from(
Arc::new(UInt64Array::from(
indices
.iter()
.map(|i| i.as_usize() as u64)
Expand All @@ -245,13 +258,12 @@ fn list_view_reverse<O: OffsetSizeTrait>(
.collect::<Vec<_>>(),
))
};
let values_reversed = take(&values, &indices_array, None)?;

let values = take(&values, &indices_array, None)?;
Ok(Arc::new(GenericListViewArray::<O>::try_new(
Arc::clone(field),
ScalarBuffer::from(new_offsets),
ScalarBuffer::from(new_sizes),
values_reversed,
values,
array.nulls().cloned(),
)?))
}
Expand All @@ -261,30 +273,29 @@ fn fixed_size_array_reverse(
field: &FieldRef,
) -> Result<ArrayRef> {
let values = array.values();
let original_data = values.to_data();
let capacity = Capacities::Array(original_data.len());
let mut mutable =
MutableArrayData::with_capacities(vec![&original_data], false, capacity);
let value_length = array.value_length() as usize;
let mut indices: Vec<u64> = Vec::with_capacity(values.len());

for row_index in 0..array.len() {
// skip the null value
if array.is_null(row_index) {
mutable.extend(0, 0, value_length);
indices.push(0);
continue;
}
let start = row_index * value_length;
let end = start + value_length;
for idx in (start..end).rev() {
mutable.extend(0, idx, idx + 1);
indices.push(idx as u64);
}
}

let data = mutable.freeze();
// Materialize values from underlying array with take
let indices_array: ArrayRef = Arc::new(UInt64Array::from(indices));
let values = take(&values, &indices_array, None)?;
Ok(Arc::new(FixedSizeListArray::try_new(
Arc::clone(field),
array.value_length(),
arrow::array::make_array(data),
values,
array.nulls().cloned(),
)?))
}
Expand Down
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