rluvaton commented on code in PR #9711:
URL: https://github.com/apache/arrow-rs/pull/9711#discussion_r3143225188
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arrow-buffer/src/buffer/offset.rs:
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@@ -238,6 +238,97 @@ impl<O: ArrowNativeType> OffsetBuffer<O> {
pub fn ptr_eq(&self, other: &Self) -> bool {
self.0.ptr_eq(&other.0)
}
+
+ /// Check if any null positions in the `null_buffer` correspond to
+ /// non-empty ranges in this [`OffsetBuffer`].
+ ///
+ /// In variable-length array types (e.g., `StringArray`, `ListArray`),
+ /// null entries may or may not have empty offset ranges. This method
+ /// detects cases where a null entry has a non-empty range
+ /// (i.e., `offsets[i] != offsets[i+1]`), which means the underlying
+ /// data buffer contains data behind nulls.
+ ///
+ /// This matters because unwrapping (flattening) a list array exposes
+ /// the child values, including those behind null entries. If null
+ /// entries point to non-empty ranges, the unwrapped values will
+ /// contain data that may not be meaningful to operate on and could
+ /// cause errors (e.g., division by zero in the child values).
+ ///
+ /// Returns `false` if `null_buffer` is `None` or contains no nulls.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use arrow_buffer::{OffsetBuffer, ScalarBuffer, NullBuffer};
+ /// // Offsets where null at index 1 has an empty range (3..3)
+ /// let offsets = OffsetBuffer::new(ScalarBuffer::<i32>::from(vec![0, 3,
3, 6]));
+ /// let nulls = NullBuffer::from(vec![true, false, true]);
+ ///
assert!(!offsets.is_there_null_pointing_to_non_empty_value(Some(&nulls)));
+ ///
+ /// // Offsets where null at index 1 has a non-empty range (3..7)
+ /// let offsets = OffsetBuffer::new(ScalarBuffer::<i32>::from(vec![0, 3,
7, 10]));
+ /// let nulls = NullBuffer::from(vec![true, false, true]);
+ ///
assert!(offsets.is_there_null_pointing_to_non_empty_value(Some(&nulls)));
+ /// ```
+ ///
+ /// # Panics
+ ///
+ /// Panics if the length of the `null_buffer` does not equal `self.len() -
1`.
+ pub fn is_there_null_pointing_to_non_empty_value(
Review Comment:
renamed to `has_non_empty_nulls`
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