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Merged
merged 6 commits into from
Nov 9, 2025
+138 −55
Merged

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
ca9319e
Add test with empty arrays
vegarsti Nov 6, 2025
41e1044
Reverse indices directly for FixedSizeList
vegarsti Nov 6, 2025
388ab48
Rework benchmark to have variable sized arrays and nulls
vegarsti Nov 8, 2025
80888ea
Merge branch 'main' into improve-perf-list-reverse
vegarsti Nov 9, 2025
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76 changes: 56 additions & 20 deletions datafusion/functions-nested/benches/array_reverse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ use std::{hint::black_box, sync::Arc};
use crate::criterion::Criterion;
use arrow::{
array::{ArrayRef, FixedSizeListArray, Int32Array, ListArray, ListViewArray},
buffer::{OffsetBuffer, ScalarBuffer},
buffer::{NullBuffer, OffsetBuffer, ScalarBuffer},
datatypes::{DataType, Field},
};
use datafusion_functions_nested::reverse::array_reverse_inner;
Expand All @@ -34,44 +34,80 @@ fn array_reverse(array: &ArrayRef) -> ArrayRef {
}

fn criterion_benchmark(c: &mut Criterion) {
// Construct large arrays for benchmarking
let array_len = 100000;
let step_size: usize = 1000;
let offsets: Vec<i32> = (0..array_len as i32).step_by(step_size).collect();
// Create array sizes with step size of 100, starting from 100.
let number_of_arrays = 1000;
let sizes = (0..number_of_arrays)
.map(|i| 100 + i * 100)
.collect::<Vec<i32>>();

// Calculate the total number of values
let total_values = sizes.iter().sum::<i32>();

// Calculate sizes and offsets from array lengths
let offsets = sizes
.iter()
.scan(0, |acc, &x| {
let offset = *acc;
*acc += x;
Some(offset)
})
.collect::<Vec<i32>>();
let offsets = ScalarBuffer::from(offsets);
let sizes: Vec<i32> = vec![step_size as i32; array_len / step_size];
let values = (0..array_len as i32).collect::<Vec<i32>>();
// Set every 10th array to null
let nulls = (0..number_of_arrays)
.map(|i| i % 10 != 0)
.collect::<Vec<bool>>();

let values = (0..total_values).collect::<Vec<i32>>();
let values = Arc::new(Int32Array::from(values));

// Create ListArray and ListViewArray
let nulls_list_array = Some(NullBuffer::from(
nulls[..((number_of_arrays as usize) - 1)].to_vec(),
));
let list_array: ArrayRef = Arc::new(ListArray::new(
Arc::new(Field::new("a", DataType::Int32, false)),
OffsetBuffer::new(offsets.clone()),
Arc::new(Int32Array::from(values.clone())),
None,
values.clone(),
nulls_list_array,
));
let fixed_size_list_array: ArrayRef = Arc::new(FixedSizeListArray::new(
Arc::new(Field::new("a", DataType::Int32, false)),
step_size as i32,
Arc::new(Int32Array::from(values.clone())),
None,
let nulls_list_view_array = Some(NullBuffer::from(
nulls[..(number_of_arrays as usize)].to_vec(),
));
let list_view_array: ArrayRef = Arc::new(ListViewArray::new(
Arc::new(Field::new("a", DataType::Int32, false)),
offsets,
ScalarBuffer::from(sizes),
Arc::new(Int32Array::from(values)),
None,
values.clone(),
nulls_list_view_array,
));

c.bench_function("array_reverse_list", |b| {
b.iter(|| array_reverse(&list_array))
});

c.bench_function("array_reverse_fixed_size_list", |b| {
b.iter(|| array_reverse(&fixed_size_list_array))
});

c.bench_function("array_reverse_list_view", |b| {
b.iter(|| array_reverse(&list_view_array))
});

// Create FixedSizeListArray
let array_len = 1000;
let num_arrays = 5000;
let total_values = num_arrays * array_len;
let values = (0..total_values).collect::<Vec<i32>>();
let values = Arc::new(Int32Array::from(values));
// Set every 10th array to null
let nulls = (0..num_arrays).map(|i| i % 10 != 0).collect::<Vec<bool>>();
let nulls = Some(NullBuffer::from(nulls));
let fixed_size_list_array: ArrayRef = Arc::new(FixedSizeListArray::new(
Arc::new(Field::new("a", DataType::Int32, false)),
array_len,
values.clone(),
nulls.clone(),
));
c.bench_function("array_reverse_fixed_size_list", |b| {
b.iter(|| array_reverse(&fixed_size_list_array))
});
}

criterion_group!(benches, criterion_benchmark);
Expand Down
117 changes: 82 additions & 35 deletions datafusion/functions-nested/src/reverse.rs
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Open in desktop
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.

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@Jefffrey Jefffrey Nov 6, 2025

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It would be nice if we figured out a nicer way of doing this but I still can't figure it out 😅

Went a bit crazy with generics in attempting once but didn't pan out; but it works and the if branch isn't a big deal, though I wonder if it's more efficient to just have Int32/Int64 arrays instead of their unsigned variants to avoid needing a map -> collect 🤔

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 @@ -260,42 +272,34 @@ fn fixed_size_array_reverse(
array: &FixedSizeListArray,
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 values: &Arc<dyn Array> = array.values();

for row_index in 0..array.len() {
// skip the null value
if array.is_null(row_index) {
mutable.extend(0, 0, value_length);
continue;
}
let start = row_index * value_length;
let end = start + value_length;
for idx in (start..end).rev() {
mutable.extend(0, idx, idx + 1);
}
// Since each fixed size list in the physical array is the same size and we keep the order
// of the fixed size lists, we can reverse the indices for each fixed size list.
let mut indices: Vec<u64> = (0..values.len() as u64).collect();
for chunk in indices.chunks_mut(array.value_length() as usize) {
chunk.reverse();
}

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(),
)?))
}

#[cfg(test)]
mod tests {
use crate::reverse::list_view_reverse;
use crate::reverse::{fixed_size_array_reverse, list_view_reverse};
use arrow::{
array::{
AsArray, GenericListViewArray, Int32Array, LargeListViewArray, ListViewArray,
OffsetSizeTrait,
AsArray, FixedSizeListArray, GenericListViewArray, Int32Array,
LargeListViewArray, ListViewArray, OffsetSizeTrait,
},
buffer::{NullBuffer, ScalarBuffer},
datatypes::{DataType, Field, Int32Type},
Expand All @@ -312,6 +316,13 @@ mod tests {
.collect()
}

fn fixed_size_list_values(array: &FixedSizeListArray) -> Vec<Option<Vec<i32>>> {
array
.iter()
.map(|x| x.map(|x| x.as_primitive::<Int32Type>().values().to_vec()))
.collect()
}

#[test]
fn test_reverse_list_view() -> Result<()> {
let field = Arc::new(Field::new("a", DataType::Int32, false));
Expand Down Expand Up @@ -450,4 +461,40 @@ mod tests {
assert_eq!(expected, reversed);
Ok(())
}

#[test]
fn test_reverse_fixed_size_list() -> Result<()> {
let field = Arc::new(Field::new("a", DataType::Int32, false));
let values = Arc::new(Int32Array::from(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]));
let result = fixed_size_array_reverse(
&FixedSizeListArray::new(
field,
3,
values,
Some(NullBuffer::from(vec![true, false, true])),
),
&Arc::new(Field::new("test", DataType::Int32, true)),
)?;
let reversed = fixed_size_list_values(result.as_fixed_size_list());
let expected = vec![Some(vec![3, 2, 1]), None, Some(vec![9, 8, 7])];
assert_eq!(expected, reversed);
Ok(())
}

#[test]
fn test_reverse_fixed_size_list_empty() -> Result<()> {
let field = Arc::new(Field::new("a", DataType::Int32, false));
let empty_array: Vec<i32> = vec![];
let values = Arc::new(Int32Array::from(empty_array));
let nulls = None;
let fixed_size_list = FixedSizeListArray::new(field, 3, values, nulls);
let result = fixed_size_array_reverse(
&fixed_size_list,
&Arc::new(Field::new("test", DataType::Int32, true)),
)?;
let reversed = fixed_size_list_values(result.as_fixed_size_list());
let expected: Vec<Option<Vec<i32>>> = vec![];
assert_eq!(expected, reversed);
Ok(())
}
}