nevi-me commented on a change in pull request #8170:
URL: https://github.com/apache/arrow/pull/8170#discussion_r489622312
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File path: rust/arrow/src/compute/kernels/take.rs
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@@ -166,42 +166,124 @@ fn take_primitive<T>(values: &ArrayRef, indices:
&UInt32Array) -> Result<ArrayRe
where
T: ArrowPrimitiveType,
{
- let mut builder = PrimitiveBuilder::<T>::new(indices.len());
- let a = values.as_any().downcast_ref::<PrimitiveArray<T>>().unwrap();
- for i in 0..indices.len() {
- if indices.is_null(i) {
- // populate with null if index is null
- builder.append_null()?;
- } else {
- // get index value to use in looking up the value from `values`
- let ix = indices.value(i) as usize;
- if a.is_valid(ix) {
- builder.append_value(a.value(ix))?;
- } else {
- builder.append_null()?;
+ let data_len = indices.len();
+
+ let array = values.as_any().downcast_ref::<PrimitiveArray<T>>().unwrap();
+
+ let num_bytes = bit_util::ceil(data_len, 8);
+ let mut null_buf = MutableBuffer::new(num_bytes).with_bitset(num_bytes,
false);
Review comment:
Is the change worth it? We can also try it on bool and numeric arrays.
If you have 35 values in take, and num_bytes = 5, you can create a range
`((35 - 1)..(num_bytes * 8)).for_each(|i| unset_bit);`I'll play with
godbolt.org to see if the compiler is smart enough to use BMI instructions for
the above range.
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