chloro-pn commented on code in PR #6178:
URL: https://github.com/apache/arrow-rs/pull/6178#discussion_r1709725449
##########
arrow-select/src/filter.rs:
##########
@@ -707,6 +710,62 @@ fn filter_byte_view<T: ByteViewType>(
GenericByteViewArray::from(unsafe { builder.build_unchecked() })
}
+fn filter_fixed_size_binary(
+ array: &FixedSizeBinaryArray,
+ predicate: &FilterPredicate,
+) -> FixedSizeBinaryArray {
+ let values: &[u8] = array.values();
+ let value_length = array.value_length() as usize;
+ let calcualte_offset_from_index = |index: usize| index * value_length;
+ let buffer = match &predicate.strategy {
+ IterationStrategy::SlicesIterator => {
+ let mut buffer = MutableBuffer::with_capacity(predicate.count *
value_length);
+ for (start, end) in SlicesIterator::new(&predicate.filter) {
+ buffer.extend_from_slice(
+
&values[calcualte_offset_from_index(start)..calcualte_offset_from_index(end)],
+ );
+ }
+ buffer
+ }
+ IterationStrategy::Slices(slices) => {
+ let mut buffer = MutableBuffer::with_capacity(predicate.count *
value_length);
+ for (start, end) in slices {
+ buffer.extend_from_slice(
+
&values[calcualte_offset_from_index(*start)..calcualte_offset_from_index(*end)],
+ );
+ }
+ buffer
+ }
+ IterationStrategy::IndexIterator => {
+ let iter = IndexIterator::new(&predicate.filter,
predicate.count).map(|x| {
+
&values[calcualte_offset_from_index(x)..calcualte_offset_from_index(x + 1)]
+ });
+
+ // SAFETY: IndexIterator is trusted length
+ unsafe { MutableBuffer::from_trusted_len_iter_slice_u8(iter,
value_length) }
Review Comment:
However, for a single memory copy operation, the compiler can copy multiple
bytes simultaneously by generating SIMD instructions.
For example, if you call memcpy once and copy four bytes, it is always
better or equivalent to calling memcpy four times and copying one byte each
time. Because the first scenario may be optimized by SIMD while the second
scenario is not.
I am not sure if Rust's compiler has implemented this optimization just like
C/C++ libc.
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