viirya opened a new pull request, #40043:
URL: https://github.com/apache/arrow/pull/40043
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### Rationale for this change
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We encountered an error when exchanging string array from Java to Rust
through Arrow C data interface. At Rust side, it complains that the buffer at
position 1 (offset buffer) is null. After tracing down and some debugging, it
looks like the issue is Java Arrow `BaseVariableWidthVector` class assigns an
empty offset buffer if the array is empty (value count 0).
According to Arrow
[spec](https://arrow.apache.org/docs/format/Columnar.html#variable-size-binary-layout)
for variable size binary layout:
> The offsets buffer contains length + 1 signed integers ...
So for an empty string array, its offset buffer should be a buffer with one
element (generally it is `0`).
### What changes are included in this PR?
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This patch replaces current empty offset buffer in variable-size layout
vector classes.
### Are these changes tested?
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Added test cases.
### Are there any user-facing changes?
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No
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