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perf: only encode actual list values in RowConverter (16-26 times faster for small sliced list) #7996

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Merged
alamb merged 5 commits into from
Jul 28, 2025
Merged

perf: only encode actual list values in RowConverter (16-26 times faster for small sliced list) #7996

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daf8f4c
perf: only encode actual list values in `RowConverter`
rluvaton Jul 24, 2025
2e034fe
avoid map_or as there must always be at least 1 offset
rluvaton Jul 24, 2025
4270ee7
added comment
rluvaton Jul 27, 2025
27faadd
Merge branch 'main' into perf-only-encode-actual-list-values
rluvaton Jul 27, 2025
7b2df90
Merge remote-tracking branch 'apache/main' into perf-only-encode-actu…
alamb Jul 28, 2025
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33 changes: 29 additions & 4 deletions arrow-row/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -518,12 +518,37 @@ impl Codec {
}
Codec::List(converter) => {
let values = match array.data_type() {
DataType::List(_) => as_list_array(array).values(),
DataType::LargeList(_) => as_large_list_array(array).values(),
DataType::FixedSizeList(_, _) => as_fixed_size_list_array(array).values(),
DataType::List(_) => {
let list_array = as_list_array(array);
let first_offset = list_array.offsets()[0] as usize;
let last_offset =
list_array.offsets()[list_array.offsets().len() - 1] as usize;

// values can include more data than referenced in the ListArray, only encode
// the referenced values.
list_array
.values()
.slice(first_offset, last_offset - first_offset)
}
DataType::LargeList(_) => {
let list_array = as_large_list_array(array);

let first_offset = list_array.offsets()[0] as usize;
let last_offset =
list_array.offsets()[list_array.offsets().len() - 1] as usize;

// values can include more data than referenced in the LargeListArray, only encode
// the referenced values.
list_array
.values()
.slice(first_offset, last_offset - first_offset)
}
DataType::FixedSizeList(_, _) => {
as_fixed_size_list_array(array).values().clone()
}
_ => unreachable!(),
};
let rows = converter.convert_columns(&[values.clone()])?;
let rows = converter.convert_columns(&[values])?;
Ok(Encoder::List(rows))
}
Codec::RunEndEncoded(converter) => {
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12 changes: 8 additions & 4 deletions arrow-row/src/list.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,16 @@ pub fn compute_lengths<O: OffsetSizeTrait>(
rows: &Rows,
array: &GenericListArray<O>,
) {
let shift = array.value_offsets()[0].as_usize();

let offsets = array.value_offsets().windows(2);
lengths
.iter_mut()
.zip(offsets)
.enumerate()
.for_each(|(idx, (length, offsets))| {
let start = offsets[0].as_usize();
let end = offsets[1].as_usize();
let start = offsets[0].as_usize() - shift;
let end = offsets[1].as_usize() - shift;
let range = array.is_valid(idx).then_some(start..end);
*length += encoded_len(rows, range);
});
Expand All @@ -61,14 +63,16 @@ pub fn encode<O: OffsetSizeTrait>(
opts: SortOptions,
array: &GenericListArray<O>,
) {
let shift = array.value_offsets()[0].as_usize();

offsets
.iter_mut()
.skip(1)
.zip(array.value_offsets().windows(2))
.enumerate()
.for_each(|(idx, (offset, offsets))| {
let start = offsets[0].as_usize();
let end = offsets[1].as_usize();
let start = offsets[0].as_usize() - shift;
let end = offsets[1].as_usize() - shift;
let range = array.is_valid(idx).then_some(start..end);
let out = &mut data[*offset..];
*offset += encode_one(out, rows, range, opts)
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