jorgecarleitao commented on a change in pull request #8688:
URL: https://github.com/apache/arrow/pull/8688#discussion_r526473704
##########
File path: rust/arrow/src/compute/kernels/boolean.rs
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@@ -457,4 +517,42 @@ mod tests {
assert_eq!(true, res.value(2));
assert_eq!(false, res.value(3));
}
+
+ fn assert_array_eq<T: ArrowNumericType>(
+ expected: PrimitiveArray<T>,
+ actual: ArrayRef,
+ ) {
+ let actual = actual
+ .as_any()
+ .downcast_ref::<PrimitiveArray<T>>()
+ .expect("Actual array should unwrap to type of expected array");
+
+ for i in 0..expected.len() {
+ if expected.is_null(i) {
+ assert!(actual.is_null(i));
+ } else {
+ assert_eq!(expected.value(i), actual.value(i));
+ }
+ }
+ }
+
Review comment:
An offset is just a shift of where we consider reading a buffer. The
easiest way to motivate it: suppose that we want to slice a primitive array of
100 elements over the range `[25..75]`. The expensive way of doing this is a
`memcopy` of 50 elements. The cheap way is to declare a new array with len=50
elements starting at 25 and increase the refcount of buffer (`Arc::clone` in
Rust).
The "starting at 25" is an offset of 25 "slots", or `25 * size_of::<T>()`
bytes for a specific type T.
For bit buffers (nullability), the offset is measured in bits, not bytes.
Feel free to ping e.g. @vertexclique, @alamb or @jhorstmann , that lately have
been working (a lot) on bits - they likely know exactly the API you need for
this. :)
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