jorgecarleitao commented on a change in pull request #9235:
URL: https://github.com/apache/arrow/pull/9235#discussion_r559224772
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File path: rust/arrow/src/compute/kernels/length.rs
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@@ -30,16 +29,16 @@ where
OffsetSize: OffsetSizeTrait,
{
// note: offsets are stored as u8, but they can be interpreted as
OffsetSize
- let offsets = array.data_ref().clone().buffers()[0].clone();
+ let offsets = &array.data_ref().buffers()[0];
// this is a 30% improvement over iterating over u8s and building
OffsetSize, which
// justifies the usage of `unsafe`.
let slice: &[OffsetSize] =
&unsafe { offsets.typed_data::<OffsetSize>() }[array.offset()..];
- let lengths: Vec<OffsetSize> = slice
- .windows(2)
- .map(|offset| offset[1] - offset[0])
- .collect();
+ let lengths = slice.windows(2).map(|offset| offset[1] - offset[0]);
+
+ let mut buffer = MutableBuffer::new(0);
+ buffer.extend_from_exact_iter(lengths);
Review comment:
This is the main difference in this PR for the length: we extend from
the iterator instead of extending a vector and then memcopying the data.
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