AndreaBozzo commented on code in PR #10916:
URL: https://github.com/apache/arrow-rs/pull/10916#discussion_r3889381023
##########
arrow-array/src/ffi.rs:
##########
@@ -474,7 +474,15 @@ impl ImportedArrowArray<'_> {
length * (bits / 8)
}
(DataType::Utf8 | DataType::Binary, 2) => {
- if self.array.is_empty() {
+ // For a zero-length array at offset 0 the sole offset
describes no data,
+ // and producers do put an arbitrary value there -- see
+ // `test_empty_string_with_non_zero_offset`, whose lone offset
is 123 over
+ // an empty values buffer -- so it must not be used as a
length. Once the
+ // array offset is non-zero, the offsets up to and including
`offset`
+ // describe real preceding elements whose bytes the values
buffer still
+ // has to cover, so the length is read from the buffer as it
is for a
+ // non-empty array.
Review Comment:
sorry, i've removed the test ref
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