[GitHub] [arrow] Dandandan commented on a change in pull request #9301: ARROW-11357: [Rust]: Fix out-of-bounds reads in `take` and other undefined behavior

[GitBox <gi...@apache.org>]

Dandandan commented on a change in pull request #9301:
URL: https://github.com/apache/arrow/pull/9301#discussion_r563171151



##########
File path: rust/arrow/src/compute/kernels/take.rs
##########
@@ -269,64 +417,44 @@ fn take_primitive<T, I>(
 ) -> Result<PrimitiveArray<T>>
 where
     T: ArrowPrimitiveType,
-    T::Native: num::Num,
     I: ArrowNumericType,
     I::Native: ToPrimitive,
 {
-    let data_len = indices.len();
-
-    let mut buffer =
-        MutableBuffer::from_len_zeroed(data_len * std::mem::size_of::<T::Native>());
-    let data = buffer.typed_data_mut();
-
-    let nulls;
-
-    if values.null_count() == 0 {
-        // Take indices without null checking
-        for (i, elem) in data.iter_mut().enumerate() {
-            let index = ToPrimitive::to_usize(&indices.value(i)).ok_or_else(|| {
-                ArrowError::ComputeError("Cast to usize failed".to_string())
-            })?;
-
-            *elem = values.value(index);
+    let indices_has_nulls = indices.null_count() != 0;

Review comment:
       `> 0` might be slightly more clear here?




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