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new b5349cbc36 perf: avoid re-allocation if buffer is not shared during
`BooleanArray::take_n_true` (#10438)
b5349cbc36 is described below
commit b5349cbc3667998b0281dfad3287680e4882d4c8
Author: RIchard Baah <[email protected]>
AuthorDate: Wed Aug 19 21:27:59 2026 -0400
perf: avoid re-allocation if buffer is not shared during
`BooleanArray::take_n_true` (#10438)
# Which issue does this PR close?
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enhancements and this helps us generate change logs for our releases.
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- Closes #10251.
# Rationale for this change
If a boolean buffer is not shared we should re-use its allocation
instead of building a new builder from scratch.
<!--
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in the issue then this section is not needed.
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your changes and offer better suggestions for fixes.
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# What changes are included in this PR?
match on `into_mutable`, in the error case the old path is taken. If the
buffer can be re-used we use it directly.
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is sometimes worth providing a summary of the individual changes in this
PR.
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# Are these changes tested?
yes, existing test cover this behavior
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# Are there any user-facing changes?
no
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---------
Co-authored-by: rich-T-kid <[email protected]>
Co-authored-by: Jeffrey Vo <[email protected]>
---
arrow-array/src/array/boolean_array.rs | 43 ++++++++++++++++++++++++++++++----
1 file changed, 39 insertions(+), 4 deletions(-)
diff --git a/arrow-array/src/array/boolean_array.rs
b/arrow-array/src/array/boolean_array.rs
index 4b0a8304d4..0e5df12825 100644
--- a/arrow-array/src/array/boolean_array.rs
+++ b/arrow-array/src/array/boolean_array.rs
@@ -607,10 +607,35 @@ impl BooleanArray {
return self;
};
- let mut builder = BooleanBufferBuilder::new(len);
- builder.append_buffer(&self.values.slice(0, end));
- builder.append_n(len - end, false);
- BooleanArray::new(builder.finish(), self.nulls)
+ let bit_offset = self.values.offset();
+ let inner_buf = self.values.into_inner();
+
+ match inner_buf.into_mutable() {
+ Ok(mut mutable_buffer) => {
+ // Unique ownership: zero trailing bits in place.
+ let actual_end = bit_offset + end;
+ let raw_bytes = mutable_buffer.as_slice_mut();
+ let byte_idx = actual_end / 8;
+ let bits_to_keep = actual_end % 8;
+ if bits_to_keep == 0 {
+ raw_bytes[byte_idx..].fill(0);
+ } else {
+ raw_bytes[byte_idx] &= (1_u8 << bits_to_keep) - 1;
+ raw_bytes[byte_idx + 1..].fill(0);
+ }
+ BooleanArray::new(
+ BooleanBuffer::new(mutable_buffer.into(), bit_offset, len),
+ self.nulls,
+ )
+ }
+ Err(buf) => {
+ // Shared buffer: copy the retained prefix then pad with false.
+ let mut builder = BooleanBufferBuilder::new(len);
+ builder.append_buffer(&BooleanBuffer::new(buf, bit_offset,
end));
+ builder.append_n(len - end, false);
+ BooleanArray::new(builder.finish(), self.nulls)
+ }
+ }
}
/// Deconstruct this array into its constituent parts
@@ -1715,4 +1740,14 @@ mod tests {
assert_eq!(r.len(), 0);
assert_eq!(r.true_count(), 0);
}
+
+ #[test]
+ fn test_take_n_true_unique_buffer() {
+ // unique buffer ownership -> mutable in-place path.
+ let arr = BooleanArray::from(vec![true, false, true, true, false,
true, true]);
+ let result = arr.take_n_true(3);
+ assert_eq!(result.true_count(), 3);
+ let values: Vec<bool> = (0..result.len()).map(|i|
result.value(i)).collect();
+ assert_eq!(values, vec![true, false, true, true, false, false, false]);
+ }
}
